Need a little guidance from the gurus

It is easiest to find a 8-1/4 or 8-3/4 for an A body rather than a rear needing a cutting and fitting and/or welding. If your talented enough to measure and weld, go for it. There is a 8.8 Ford rear swap thread here that is a very very good thread to read. The Ford rear is strong and readily available.

But to keep it cheap, I think a 8-1/4 A body rear is it.

Dodge trucks and vans often have a Magnum engine. Mostly the 5.2 AKA 318. Just keep the eyes out for the 5.9 I.D. On the engine I.D. Sticker and then double check the drivers side of the block for the 360 cast into the block.