Magnum 5.2 in '72 Dart

Welcome aboard!
Good luck with this swap as it shouldn’t be to hard. I can’t help a a lot on this but.....

If you have factory disc breaks, they will do well. There are same diameter for what ever engine the car came with. If you felt they were not up to par, grab the brackets from the later year B bodies, like a Córdoba and use the larger discs and OE parts. Find some 11 inch backing plates as well. Same cars.

On the trans swap, there is a thread or two here that covers that. An A-500 would be an easier fit since it is based off the 904.