rear disc from grand cherokee on a 8 3/4

On the 8.75 we bolted the backing plate on then knocked the wheel studs out of the axle (because it is small bolt pattern) we held the rotor up against the axle hub then installed the caliper.In order for the rotor to line up propperly we had to move the rotor about 3/4 of an inch away from the hub. On the 8.25 every thing lined up perfect.
I was wondering if the fact that the 8.25 uses the c clips to hold the axles in as apposed to the flanges that keep the axles in the 8.75 might be the difference.
Wish now I would have taken some pictures of the problem with the mock up.

did you figure i nthe offset difference of sbp drums to bbp drums?