Hey 56 Chevy, my brother and his son are in the process of putting a 57 GMC shortbox 1/2 ton on a shortened 70's suburban frame. It has gone well so far. One thing they have to do is find a narrower rearend for it so the wide tires won't rub on the fenders. Your cab should be the same as thiers but your front clip is probably bigger ( wider and longer perhaps). If your handy with the welder and can fabricate stuff it shouldn't be too hard at all. Good Luck!
