I believe you could mount your cab on any year AD frame, but the bed would only fit on a 54 or 55.1 frame, as the earlier frames have a higher hump over the rear axle. I believe, but can't be 100% sure that the rear springs and mount points would interchange between a 54 with torque tube rear axle and a 55.1 open driveshaft axle.
[on edit] I just checked with Eaton Detroit Springs website and 55.1 springs are different than earlier AD, but if you already have the springs, all that's needed is for the mounting points to be the same. 54 rear springs are 8-leaf, 54 inches long, while 55.1 springs are 8 leaf, 54-1/8 inches long, per the vehicle info kit data. That's probably an inconsequential difference. The mounting point center-center dimension difference is about 1/4 inch, again probably workable.
Last edited by klhansen; 10/24/2025 6:04 PM. Reason: added info on rear springs
