you have to have the drums and axle re-drilled from 4" to 4.5" wbp

or use an early B-body 8 3/4 housing

or like I did,set of moser A-body spec axles with the large brake offset,green bearings(or a stock bearing)

they will make the whole A-body 8 3/4 rear axle a 1/2" wider(1/4" each side)

I ran a 7" rim with a 4.5 backset with a 245/60/15 on my 68Dart fit was perfect in the fender wells

FYI,I took the same A-body 8 3/4 axle and bolted it in the 88 440 truck I built to run 12" wide rims and a 29x15x15 M/T..used the same 4.5 backset tucked them right in

A-body and trucks share the same 43" spring centers

and dont forget to put some lipstick on the 8 3/4 when it goes in the A-body