So the two A-body widths are:
The small bolt 8 3/4 width and the late model A-body big bolt width.
So we know that the 1.75 wide small bolt brake backing plates wont work with a large bolt 8 3/4 axle. Because the small bolt and big bolt axles have different widths from the bearing to were the wheel bolts on. Using the big bolt axles widens the small bolt 8 3/4 width. Make'n it work with what I have, mentality.
The late model A-body have a different width, it is narrower than the small bolt 8 3/4, and allowing a 15x7 wheel to fit in a duster wheel well. This is the one I prefer because it has its advantages especially when shorting an housing.
8.75 a body BBP rears. Please do tell...
The 8.75 stopped production in 1972 SBP then swapped to the 8.25's, BBP, in 340 cars for 1973
52 5/8" flange to flange, all and every one was SBP, is the base measurement of every one I've ever had my hands on from 1967 to 1972 cars. With minor +/-
Yes, if you want an A body rear to have the same overall width (57.125) of the stocker ones, using BBP, the housing needs to be narrower to compensate for BBP increased brake stand off distance.
1972 andlater all had either the 8 1/4 or the smaller 7 1/4 rear eds in them, no SBP 8 3/4 in them after 1971 
