I have a 62 1/2 ton, and i put a 71 rear in,because i did the front member swap with disc brakes, and the 71 is 5 lug. to put the newer 12 bolt in, i had to cut off the u bolt saddles and weld new ones,the 62 trailing arms are wider apart. 63 and up is a direct bolt in. i got the saddles from CPP for 35 bucks, just be careful with the measurements and pinion angle.hope this helps.....Mark
