75 K20 203 to 205 swap

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CarterDawson

Junior Member
Joined
Mar 6, 2023
Posts
19
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16
Location
WA
First Name
Carter
Truck Year
1975
Truck Model
K-20
Engine Size
350
Hey guys, I used the search and read several threads that answered most of my questions. My truck is a 75 k20, 350/350/203. Looking to swap the 203 to a 205. I’m aware I will need different drive shafts. All that stuff is not a problem. I got connections and won’t have a problem getting the correct drive shafts. The 205 I have access to is out of a 1980 K20 with a 350/205. The trans/tcase are still paired. My question is, to my knowledge my 75 K20 should be 27 spline output, while a 80 k20 would’ve had a 32 spline? So how do I make that swap work. I don’t really want to swap transmissions as the one is my truck is super smooth. The one out of the 80 is in unknown condition. My other question is would the 80 have the slip in the transfer case, or is it in the drive shaft. I had a 80 suburban a while back with the 205. If I remember right the slip was in the transfer case. Is one better than the other?

I apologize if my terminology isn’t right. I’m trying to say everything correctly, but is kinda a lot to remember for a novice like myself. Thanks for your patience.

I apologize if I'm asking questions have been answered in previous threads. If so I would appreciate any links. And help or advice is greatly appreciated. Thanks
 

SquareRoot

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Mar 18, 2017
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Location
Arizona
First Name
Mike
Truck Year
85
Truck Model
K20
Engine Size
350
Just swap the input shaft to the spline count that matches the trans. Slip in the shaft is always better. That means you have a fixed output on the trans. It's not required, depends on what you're trying to accomplish.
 

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