Tire b/s clarification!

Depends on what the length your rear is. There were many 8 3/4's made for many different body styles. Which one are you putting in yours and is it original unmolested length? A body 8 3/4, you'll likely need what these other guys have suggested as far as 4.5" b.s., but if your using a 65-70 B body 8 3/4, then you'll likely need 5" b.s. (my 71 Dart Swinger with B body 8 3/4 needed 5 1.4" b.s. or else a 5" b.s. with an 8 inch rim and 225/50 15 with the wheel lip rolled on both quarter wheel openings.) My 73 Dart Swinger wasnt happy with the B bod 8 3/4 with 5" b.s. and 15x8 rim with 245/60 15 Yokohama's, so I narrowed the rear 3/4" on each side, then it was ok with 5" but woulda been much happier with a 5 1/4" b.s. as they still "JUST" rub the lower part of the sidewall on the drivers side higher up in the wheel well. Both cars had EHD springs that were new.