Looking for some advice on a 360 magnum swap

If it runs, drop it in. I like the serpentine belt. Get the b van power steering bracket and the idler to toss the AC and you're set.

You'll need a magnum compatible intake for that carb.
I was looking at the crosswind intake, although it all depends how the factory heads are on the magnum. If they are cracked I'll probably go with new eq heads and be able to use my weiand action plus intake I already own