I don't mean to be the one to knock the wind out of your sails, but the cooling difference between aluminum and copper is negligible, as a little research would have shown. Here are two articles that discuss the differences and show copper/brass are far superior to aluminum.
Scroll down a little to find the aluminum vs. copper/brass radiator info on this page copper.org
then there is this site USradiator
Aluminum is pushed by to many who do not realize or know the differences between the materials. Having studied metalurgy I gained a little insight into the subject. Also, something that I don't recall being mentioned in either of these articles but something that DOES affect all of us running the old iron blocks is a process called galvanic corrosion, I won't go into the science here but suffice to say that aluminum to steel galvanic corrosion is much greater than copper/brass to steel in an ethylene/glycol cooling system. And yes, this does matter in the long run for the guys running aluminum heads and intakes also. What I will say is that if you are running aluminum parts in your cooling system, whether heads, intake, radiators or what not, replace coolant annualy and definatly use Water Wetter™ as it helps protect the aluminum parts from this type of corosion.
