What were the 11" rear brake widths for Mopar?

The backing plates are different for each of the three widths. So, if you have 11x2.5" backing plates, you can't use them with 11x2" or 11x3" shoes or drums or vice versa.

The backing plates have to be different because the axle flange offset is the same for all of the BBP axles. Since the face of the drum is in the same spot, the backing plate has to be unique to the width of the brake shoe.