m376x6

No, but not a major obstacle. The 8 3/4" diffs were 2 pinion, while the 9 5/8 were 4 pinion diffs. The diameter of the shafts are the same at 1 3/8 10 spline. The actual shaft is 1 1/4 inch between flange and splines. The difference in 8 3/4 and 9 5/8 shafts is the length. The 8 3/4 is 36 17/64 while the 9 5/8 is 36 15/64. If you are using a 8 5/8 diff either shaft will work. If trying to use a 8 3/4 diff shaft in the 9 5/8 diff you will need to grind off 1/32 of an inch. Based on your description, the shafts you have found will work. That small difference in length won't be any disadvantage unless you start using high torque/horsepower engines. Check the housing to make sure there are no tags welded to it instructing you to use 2 carrier gaskets instead of one. Best of luck.

Regards,
M376X6