Copper and brass will, if in good shape, transfer more heat into the air stream than aluminum will.
I went through this with my old pump gas car, the new aluminum cooled better for one summer and then did worse the next summer puke
I had put 50% anti freeze in both but the aluminum lost it ability to shed heat into the air stream over the winter work
I took it to a radiator shop and they did something to make it work for that summer and it did the same thing the next winter shruggy
I will only buy copper and brass now up

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)