Pros and cons of using a B-body rear axle assembly???

On Dusters, Demons and Dart Sports you will not need custom wheels or to narrow the axle housing if you purchase a 70 and prior B-body axle; it may be the same on A-body Barracudas as well. As for no dish, that would only be if a later than 70 was used. On my Duster I was able to run 10" wide rear wheels with 6.5 backspacing on a stock width B-body Dana. I had similar wheels on my Dart Sport with a stock width B-body 8 3/4. The wheels were not custom; I have seen many sets with that same backspacing at numerous swap meets. Hell, if you decide to get new you can just order them with whatever backspacing you want anyway.

The biggest benefit is if you somehow break an axle shaft, you just go get another; no need to have a custom axle shaft made to fit your custom housing.