Dan,
3B and Spanky are good members to appeal to. Wait to hear from them.
I have recently put new bushings and pads in a 54/55 2-ton GMC COE which could very likely be different.
I was lucky that the rubber bushings and the two forward mounting-bolts were the same size as used in the 1954 3100 cab mounts (I had 3 different mounting kits for that size/year truck).
The large thick rubber/composition pad between the front cab and the frame perch for the front of the cab was the same dimensions as used on the pickup. However, I had 3100 mounting kits from different vendors, and the size (length/width of the square) of the pads differed between kits.
The shackle bars and bolts were different. The 3100 shackles had two plates and two bolts. The 54/55 COE shackles had one plate with holes and the other plate with two bolts integral to the plate. There was a metal ferrule over each bolt and the rubber bushings fit over the ferrules. I was able to use the bushings with my old rear shackle hardware.
I'll double check and post corrections, if I am wrong.
