FUEL TANK CAPACITY 1982 K10 4x4

[Beast496]

Except the unusable fuel is just that, so it doesn’t matter.
I am pleasantly surprised though that virtually 100% of the stated capacity is useable in these trucks though.
In testing both the 77 and 86, I can run it down to where the needle doesn’t bounce up off E at all and have put 19.xx gal in the 20 gal tanks, prior to actually running out of gas.

I'm in the process of testing this theory as I just replaced my fuel gauge, cleaned a bunch of grounds, so both tanks are reading what I assume is correct now. Will be going until I run one tank out(or as far as I feel comfortable), then see what it takes. Then the same for the other side. Thankfully, the big block loves to drink fuel so shouldn't take too long, lol.

 

[75gmck25]

The older tanks are not baffled, so how low on fuel you can go may depend on the angle of the truck and whether you are turning a corner. I was running low on one tank and turned a corner that also went up hill and the truck suddenly quit. Switched tanks and it started right up. That fuel can slosh quite a bit. Baffles in the 87 and up tanks are supposed to help.

 

[Frankenchevy]

OP, the length is a pretty clear indicator. If the rearmost tank strap is close to the filler neck end, you have a 16 gallon tank.

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However, if there’s a foot or so between the rear strap and filler neck, you have a 20 gallon.

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[83Stepper]

Overall lengths will tell you, quickest and easiest way to distinguish the 16 or 20 gallon tanks from themselves. Never ran across an OEM unit on these trucks with a drain plug. My 63 Galaxie 500 had a drain plug in the tank, but I don't recall ever seeing a GM product with a drain plug on any of the vehicles I've owned. The 16 gallon tanks are like 42" long and believe the 20 gallon tanks are like 56" iirc.