How do I find an 8 3/4 rear in the jy

Let’s clear up some misinformation here….

The last year for an 8 3/4” in an A body was 1972

1973 and later cars could have a 7 1/4” with small bolt or large bolt, small bolt for drum brakes up front, large bolt for disc brakes. High performance A bodies in 1973 and later came with disc brakes and the 8 1/4”

The easiest way to check to see if an A body has an 8 3/4” without being able to look under it would be to inspect the brake backing plates. It would have small bolt pattern lugs and 5 studs and nuts to hold on the backing plates, 7 1/4” only had 4. Of course, anything could be changed up over the years, but this is how they came from the factory.