bbp axle change what backing plates are needed

as others have said,
it depends on what axles you get.

I bought mine from Moser, first thing they asked, was if I wanted A-body offset, or B-body offset.
I bought the A-body offset axles, which allowed me to keep my original backing plates, brakes, and drums. Just had to redrill the drum for the bigger 5-lug pattern.