First off is it the original rear in the car...if it is it will be small bolt pattern and prob 10" drums...they stopped 8 3/4 in a bodys in 72.If its large bolt pattern..5 on 4.5 it is not factory to the car..could be B,E body.
That or someone at some point swap out the axleshafts to go to the Big Bolt Pattern i.e. and aftermarket set of moser a body axleshafts with the BBP instead of the SBP.