A friend of mine wants me to buy his 4X4 1968 GMC 3/4 ton because it's rusting to the ground. Because of the rust, I don't trust his frame either, but I'm mainly interested in his 4WD and suspension. So I've thought about it, but decided rather than to put my body on his frame, instead to put his suspension and axles on my frame and make the necessary adjustments.

Any shop that works on rear ends should be able to help you narrow yours. That is a common thing with musclecars so that they can get big meaty rubber under their wheel wells.

If you do end up using your frame, I'd suggest a little strengthening of the frame while you're at it. Couldn't hurt. Maybe cross brace it.

52 GMC 3/4 ton pickup
68 Big Block Vette
68 455 Firebird