GMT800 NBS seats in a Square Body....

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Old77

Administrator
Staff member
Admin
Joined
Aug 19, 2010
Posts
28,220
Reaction score
8,590
Location
Kansas City, Mo
First Name
Jacob
Truck Year
1977/1990/1991
Truck Model
C10 longbed/R1500 Burb/R3500 Dually
Engine Size
350/350/454
Not sure if this is worthy of making a "Sticky" but maybe one of the higher ups can make that decision.....

Inquiries are becoming more and more prevalent as to how to get seats out of a NBS (99-06) truck to fit in our square bodies so I thought I’d do a little write up on what I did in order to get this mod to work and the seats to fit correctly. The casual observer initially thinks they’ll just fit right in with just slight modifications but that is far from the truth!! There are two ways you can tackle this install so let’s explore both. I’ll start with the method that I did NOT go with first and finish off with how I tackled the project.

Disclaimer: Keep in mind this was done on a ’77 C-10 which is a 2wd cab. I understand there are some differences between the 2wd and 4wd cab but the concept should generally be the same. You will want to take these differences into account for your project.

1. You could modify the seats to fit. At first glance, it appears that just modifying the seat brackets will make the seats fit and will be an easier way to go about making them fit. There are a couple of issues with this method...
a. You need to create at least 6 to 8 inches worth of clearance in order to get the seat to fit under the steering wheel. There’s no way to modify the existing bracket in the seat to make this happen and create this much space. If you look in the photo below that shows the floor prior to modification there’s a slope towards the rear. This slop is what largely prevents this method from working.
b. If modifying the seat was possible, due to the amount of customization you’d have to do to the brackets on the seat you’d lose the functionality of being able to move the seat back and forth on its track. If you had leather seats with heat you’d probably lose this functionality as well in order to create more room.
c. Even if you were successful in cutting down the seat bracket you have to figure out a way to finish off the side of the seats for the couple of levers that are on each side.

So based on these factors, and I’m sure others that I’m forgetting 6 years after the fact, we decided to go with route #2.

2. Cut down the floor which essentially removes the humps where the gas tank(s) are usually located under the cab and relocate the gas tank. The relocating of the tank is pretty straight forward. We just bought a new tank that’d normally go into a 73-89 blazer/Suburban and fit it between the frame rails at the rear of the truck. The only fabrication that had to be done was for the new filler neck location and mounting spots for the tank straps. I’m sure there are numerous ideas for relocating the tank. If I was to do it over it again (and I might as some point) I’d get a flip down license plate and get a different tank that’d allow me to fill up at that location.

The hardest and more time consuming part is the modification that needs to be done to the floor. Take your time here! You want to measure several times before one cut is ever made. We measured several times, drew our cut lines on the floor and measured again prior to cutting. You will have to leave a small “hump” on each side due to the frame but this does not hinder the seat location at all. At this point, I don’t remember the exact measurements but hopefully the pics will give you a good idea. Even if I had the measurements I’d strongly encourage you take your own measurements just to ensure they were accurate for your truck. Starting in front of that “ledge” that comes out from the back wall, I would cut as much out of the floor as possible to make the seats fit because you’ll need all the room you can get. This is one of the reasons I ended up with a billet steering wheel because it was slightly smaller than the original and gave us a couple more inches clearance for driving comfort. Again, the frame will limit how much you can cut out (at least for the 2wd models) so we just cut out as much as we could and left the small humps for the curvature of the frame.

Before
You must be registered for see images attach


Now time for some cutting!! :superhack:

NOTE: As a precautionary measure, before any cuts were made we braced the cab near the roof just to prevent and “sagging”. Because I had some laying around I just used two 4x4 pieces of wood in a “T” formation but you could do this a multitude of ways by tack welding metal in or however is easiest for you.

After the holes are cut in the floor, you’ll need to fab up the floor pans. At this point I forget what gauge of steel I used but you should get a gauge that closely matches that of factory steel. These pieces should be pretty straight forward to create but again you’ll need to measure and then bend the metal accordingly and then welding the corner seams together prior to putting it in the cab. You will want to do a test fit of the pieces in the cab by tack welding them in, place the seats on the new panels and mark where you want the seats to fit in order to drill holes in the panels prior to permanently installing the panels. Once you’ve accurately marked the holes take the new panels back out and drill the holes. Along the strip where the bolts will be a strip of metal about 3” wide was welded in just for added bracing just in case of accident. Might have been overkill but I’d rather it be extra strong :) Once the holes are drilled the nut was tack welded on the under side. You need to be very careful here because the heat of the welding could mess up the thread of the nut. We tack welded them in only to make it easier for one person to bolt/unbolt the seats at any given time but if going this route is not absolutely necessary. At this point, the new panels are ready to be put in permanently.

During
You must be registered for see images attach

You must be registered for see images attach



After everything was in and finished off, I undercoated the entire underside of the cab (along with the rest of the undercarriage of the truck) in POR-15 to prevent rust from forming in the future. There are several products you can use to accomplish the same thing but I liked the POR-15 and how it came out in the end. The downside to this stuff is if it gets on your skin it’s extremely hard to wash off and impossible if you don’t get it off immediately after it makes contact with your skin so I usually just covered myself with clothing from head to toe! :) Once the undercoating was complete I just threw those clothes away because they were essentially ruined :)

Once the mod is complete and the seats and carpet are installed no one will know what level of work it took to get the job done until you point it out to them. Everyone who looks at my seats at any cruise or show just opens the door and says, “Boy, those fit in there pretty good don’t they? Did they just bolt right in??”. This is the kind of response I look for when doing any mod. Subtle is what you want! :)

After
You must be registered for see images attach


Sorry for the bad quality of that last pic. It’s a cell phone pic. I will try and get a better pic(s) posted up of the finished product. If I can scrounge up better pics of the process I will certainly post them up by editing this original post so that I can keep it all together. These are all I could find at the moment but there may be more on my other computer.

Hopefully this will give you a good idea of what is involved. Don’t hesitate to post up any questions or comments!!!

:driver:
 
Last edited:

nxtlevl

Full Access Member
Joined
Nov 4, 2010
Posts
518
Reaction score
11
Location
Hutchinson,KS
First Name
Ed
Truck Year
1987
Truck Model
C10
Engine Size
350
Nice write-up.....:High 5: A lot of work, but the end results look well worth it.
 

Manbearpig

Supporting Member
Supporting Member
Joined
Jul 30, 2010
Posts
1,685
Reaction score
14
Location
Midland, Tx
First Name
Tyler
Truck Year
2003
Truck Model
1500HD Quadrasteer
Engine Size
6.0
Great job man!

I didn't know they were that difficult to get in there
 

Old77

Administrator
Staff member
Admin
Joined
Aug 19, 2010
Posts
28,220
Reaction score
8,590
Location
Kansas City, Mo
First Name
Jacob
Truck Year
1977/1990/1991
Truck Model
C10 longbed/R1500 Burb/R3500 Dually
Engine Size
350/350/454
Thanks! I didn't either until I bought them, had them in my garage and start to test fit. Prior to the project the top of the seats would literally but up against the original steering wheel. I guess, in most cases, where there's a will there is a way if you want to make something work bad enough :)
 

85k10383

Full Access Member
Joined
Jul 31, 2010
Posts
374
Reaction score
7
Location
Glengary, WV
First Name
Ross
Truck Year
1985
Truck Model
K10 Scottsdale
Engine Size
383
Very nicely done! And a concise description of what was needed to make the seats work, Kudos to you man! I may have to look at doing this more seriously as my floors are in pretty sad shape already.
 

Old77

Administrator
Staff member
Admin
Joined
Aug 19, 2010
Posts
28,220
Reaction score
8,590
Location
Kansas City, Mo
First Name
Jacob
Truck Year
1977/1990/1991
Truck Model
C10 longbed/R1500 Burb/R3500 Dually
Engine Size
350/350/454
Sounds like a plan to me! I did the front floor pans first as they were all rusted out (surprise, surprise) then moved on to the seat project. It was definitely well worth it in the end! If you do it and have any questions along the way just ask man!
 

Jaymez

Full Access Member
Joined
Jul 30, 2010
Posts
719
Reaction score
15
Location
Connecitcut
First Name
Jim
Truck Year
1987
Truck Model
V10
Engine Size
350
Awesome write up, man. When are you coming out to do mine?
 

Old77

Administrator
Staff member
Admin
Joined
Aug 19, 2010
Posts
28,220
Reaction score
8,590
Location
Kansas City, Mo
First Name
Jacob
Truck Year
1977/1990/1991
Truck Model
C10 longbed/R1500 Burb/R3500 Dually
Engine Size
350/350/454
haha!! If you were closer I'd definitely be anxious to help out. I really enjoyed it and learned a TON while doing it. We got lots o' jobs in the Mo/Ks area if that is enticing to ya and the Missus. :D
 

CknightK10

Full Access Member
Joined
Dec 13, 2010
Posts
389
Reaction score
16
Location
California
First Name
Chris
Truck Year
1985
Truck Model
K10
Engine Size
5.7
sweeeet!! :crazy: soo I am considering doing NBS seats, and I have been for a while. What my plan was, to first off, get my NBS seats, then to find a stock OBS bench seat. Then I figured I could take off the NBS seat brackets completely and mount the NBS seats to the bench seat bracket. Now from your experience, does this sound do-able????? Thanks!
 

Old77

Administrator
Staff member
Admin
Joined
Aug 19, 2010
Posts
28,220
Reaction score
8,590
Location
Kansas City, Mo
First Name
Jacob
Truck Year
1977/1990/1991
Truck Model
C10 longbed/R1500 Burb/R3500 Dually
Engine Size
350/350/454

Old77

Administrator
Staff member
Admin
Joined
Aug 19, 2010
Posts
28,220
Reaction score
8,590
Location
Kansas City, Mo
First Name
Jacob
Truck Year
1977/1990/1991
Truck Model
C10 longbed/R1500 Burb/R3500 Dually
Engine Size
350/350/454
sweeeet!! :crazy: soo I am considering doing NBS seats, and I have been for a while. What my plan was, to first off, get my NBS seats, then to find a stock OBS bench seat. Then I figured I could take off the NBS seat brackets completely and mount the NBS seats to the bench seat bracket. Now from your experience, does this sound do-able????? Thanks!

I'm going to assume you meant OOBS bench seat, right??

If so, I can't tell for sure it won't work cuz it just might. We did not look into this route, though, to give you a 100% for sure answer on this. If I was going to throw out an educated guess, though, I would say no. The reason for this is due to the design of the bench seat bracket for the OOBS and the NBS seats. The rear part of the floor goes up at such a steep grade that I think you'd still have to modify the seats pretty heavily to get the bracket to fit correctly. Then you gotta worry about losing the functionality of the seat going back and forth and leaning up and back.

If it was me and I were you I'd go ahead and get the NBS seats and look into your idea. After a few measurements you should know pretty quickly. If your idea won't wohe's then you have another avenue on this thread that will for sure work.

If your idea does work then definitely post it up on this thread so that others have two valid methods for this mod :waytogo:

so short answer to you question I'm not 100% for sure:)
 

crazy4offroad

Equal Opportunity Destroyer
Joined
Jul 30, 2010
Posts
8,468
Reaction score
1,068
Location
West BY-GOD Virginia
First Name
Curt
Truck Year
1979
Truck Model
K-10
Engine Size
350/SM465/NP205
I used the bench seat brackets that bolt to the floor and some angle iron from some old bed rails to make a basic frame, and bolted some Subaru bucket seats to it. It worked pretty good but sat a couple inches higher so if you're really tall it might not have worked so good for you. But it was nice being able to see over that 2-acre hood on the trails. One bad bounce though and your head gets smacked on the roof. I swapped it out for the old bench seat though so I could have 3 people up front, and my honey could scoot over close to me while we were wheelin. But I made a homemade center seat with a console under it for starage for that thing, and a fold-down back with homemade cup holders in it, I'll have to get a pic or two of it next time I'm up mom's.
 

Old77

Administrator
Staff member
Admin
Joined
Aug 19, 2010
Posts
28,220
Reaction score
8,590
Location
Kansas City, Mo
First Name
Jacob
Truck Year
1977/1990/1991
Truck Model
C10 longbed/R1500 Burb/R3500 Dually
Engine Size
350/350/454
Yeah, I'm 6'3" so I'm pretty sure the Subaru seat set up wouldn't work for me :) the NBS seats give your butt all the comfort of a newer truck and it thanks me for it!! :) plus you get the integrated seat belts which is the reason I originally wanted to do the mod ;)
 

CknightK10

Full Access Member
Joined
Dec 13, 2010
Posts
389
Reaction score
16
Location
California
First Name
Chris
Truck Year
1985
Truck Model
K10
Engine Size
5.7
I'm going to assume you meant OOBS bench seat, right??

If so, I can't tell for sure it won't work cuz it just might. We did not look into this route, though, to give you a 100% for sure answer on this. If I was going to throw out an educated guess, though, I would say no. The reason for this is due to the design of the bench seat bracket for the OOBS and the NBS seats. The rear part of the floor goes up at such a steep grade that I think you'd still have to modify the seats pretty heavily to get the bracket to fit correctly. Then you gotta worry about losing the functionality of the seat going back and forth and leaning up and back.

If it was me and I were you I'd go ahead and get the NBS seats and look into your idea. After a few measurements you should know pretty quickly. If your idea won't wohe's then you have another avenue on this thread that will for sure work.

If your idea does work then definitely post it up on this thread so that others have two valid methods for this mod :waytogo:

so short answer to you question I'm not 100% for sure:)

I ment OOBS.. lol I just dont want to have to cut floors, and move tanks. Mabey someday when the truck gets painted.....
 

Latest posts

Forum statistics

Threads
41,851
Posts
903,500
Members
33,365
Latest member
rossivey
Top