HOT running mopar 360LA

I agree with 1wild&crazyguy you may just have too high compression for that type of application and the engine is putting out too much heat for the cooling system to control. You say you have non-Magnum heads, with 10:1 compression many will agree that's too much for pump gas and open chambers unless you run a big enough cam. What kind of cam does your engine have?

I think my solution would be to get the ignition timing dialed in and just start mixing race gas with premium pump when you hit the dunes... Or swap to closed-chamber heads.