I have an A body 8 3/4 to put in my 63 Valiant if the 7 1/4 ever tears up. So far it hasn't.
I had 4-5 spare 7 1/4 rears sitting around until maybe a year and a half ago, then said, Hell, I'm never gonna use these, and hauled them off for scrap, along with several tapered axle 8 3/4 rears. Them and other stuff was 2500 pounds and two pickup truck loads. Too bad scrap metal prices are so low these days.
