the stock A-body has its own axle offset and backing plates for 1 3/4" brakes with sbp

if it has been a narrowed housing and you have the large brake off set on the axle you can use any BP-drums from

8 1/4
8 3/4
9 1/4
d-60

i used 73 newport BP-drums 11x2.5 on my narrowed a-body 8 3/4 with large brake offset axles

just get BP and brake hardware from any spare axle of your size and like

I ran 12 disc(R-body cop car) on 73 a-body spindles with 11x2.5 rear brakes on my 68 Dart with the 2-bolt alum MC

stoped real fast and no locking up