Magnum 360 heads "best" for my build?

3.23 gear at the least.jmo

polish anything that might be crack prone=between valves around chamber, yes they crack there too, and you'll be good.jmo
Especially in the bowl between the valves, I've seen them crack from the seat down almost to the bowl roof.

you should be good though with what you are doing as long as you have enough capacity in the rad.