71/72 b body rear in an abody?

I don't think its a '71-72 b rear. More like a '65-'69 C body. The 61.75" drum to drum number lines up perfect with a C body rear from those years, and the 742 would match that as well.

In a Duster, the 68-70 B rear works well with 8 or 9" wide rims that have about 6" of backspace if the springs are in the stock location. But those are 60 1/8" drum to drum. With a 61.75" wide rear, you'd be looking at close to 7" of backspace. The '10-'14 Mustangs run that much, so there are rims out there if you want to go that way, but it wouldn't be my first choice.