8 3/4" rear question

Just remember that A-body 8 3/4" rears all came with a 4" bolt pattern. '73 & up A-bodies rears had 4.5" if it had disc brakes up front. Driveshaft length may change and you may have to match up the u-joints. 7 1/4" rear u-bolts & shock plates are not compatible with an 8 3/4" rear also.