Ramcharger 360

You’ve already helped yourself out tremendously by electing to install 4.56 gears and the 46RH. But, on to answering your questions on a 360 build. I like the thought of refreshed Magnum heads on a 360 with this build. But, you mentioned Black Friday sales… if you do the 40% off sale at speed master and get a set of bare aluminum heads for your engine shop to put together with the parts of their choice, you’d have a significant advantage over either iron head. Most piston choices outside of stock replacement with magnum heads are going to put you in the 9.7:1 or higher area if you build for quench with the magnum heads, while the speed masters would get you 9.4:1, which would be compatible with 87 octane fuel with judicious tuning. I would run these pistons and get the block cut for zero deck.
DODGE KB KB232KTM.040 Keith Black KB Performance Hyper Piston and Ring Kits | Summit Racing
Those figures are based on using a Mr gasket .040 thick MLS head gasket with a 4.08 inch bore. If you use magnum heads, this cam would work well (along with AMC type lifters and oil through pushrods for the magnum rocker train, of course) for a .480/.496 lift with the 1.6:1 magnum rocker ratio.
Howards Cams 710031-12 Howards Cams Street Force 2 Hydraulic Flat Tappet Camshafts | Summit Racing
If you went with the speed masters, then this cam would be my go to. You could even use this cam with the magnum heads, being you’ll have to get the Hughes type retainers and springs to make either of the cam choices to work with the magnum heads. You get .511/.526 lift with the magnum rocker ratios. It would be a real stump puller.
https://www.competitionproducts.com/mobile/Howards-Cams-Hydraulic-Flat-Tappet-Camshaft-Chrysler-SB-273-360_318-208_214-050-479_494-110-LS/productinfo/HRC711381-10/#.Y3Ej6yVOmEc
If you’re wanting to get more involved in your own build and learn something on the way, here’s the factory magnum porting templates. These are fairly conservative and don’t take the heads out to anywhere near maximum potential, but would work really well for you’re intended purpose, especially with the second cam choice and higher lift.
https://www.bigblockmopar.nl/wp-content/uploads/2016/03/MoparPortingTemplates-RB_LA_Magnum.pdf