[Mr. Creosote]

I believe aluminum is actually not as good a thermal conductor as copper. In any case, cooling will be functions of radiator size and fins per inch as well as air flow through the radiator. Increasing any of the above will remove more heat. Sometimes simple things like louvers located towards the rear of the hood and/or fenders will reduce air pressure buildup under the hood and thus allow more air to flow through the radiator when the vehicle is moving.