I would look at the factory service manual and follow the specs. it provide.
I think the 8 3/4 uses .0030 maximum run out.
I found out by accident that heating the ring gear up to or over 130F and then install it on the carrier really helps making it seat flush eliminating any ring gear to pinion tooth backlash variances up :: scope:

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)