I did a drivetrain swap using a 1980 4X4 suburban to a 1956 GMC suburban. Both trucks were 34". Keep the old frame for sure. Whole lot better. Adapt axles to frame. Wheel back spacing can help if too wide. Many components will stay on old frame (the list is a mile long). The main fab is limited to engine mount, tranny mount, steering hook up, spring hangers/shackles fab and driveshaft shortened. Both the 80 4x4 and the 1956 were leaf spring all four. Since you have both vehicles like I did, you can take both bodies off and really plan it all out looking at both frames. Keeping the straight axle (adding PS and disc) or doing a 4X4 is way easier than a clip.
