I have an '85 C10 body (originally 2wd) on a '78 GMC K (4x4) chassis. The '85 body donor truck originally had a 6.2L diesel and an automatic transmission. I don't know what model the transmission was. The '78 GMC chassis has a 350 gas V8, and originally had a 4-speed manual transmission. The 4-speed was replaced with a TH350 automatic when the chassis was paired with the '85 body. Previous owner did all the work, so I don't know what all he had to do to get everything to fit, but I do know it can be done. The 4x4 shifter is very well-integrated and looks like it was there all along.