[GuyBFF]

For radiating, not really, the reason aluminum radiates better is the fact it can't absorb as much heat as copper. In heat sinks copper is therefore used as a great conducter to get the heat off the cpu and disperse it threw the most area. Once spread out the aluminum fins do the excellent job of radiating this heat.

In a radiator the water is so close to the surface of almost all the fins, and there is really no need to spread this heat as the water is already performing this. The most thermally effecient rads are straight aluminum, as they don't absorb nearly as much heat as copper and perform much better at radiating.

I would however purchase an aluminum finned, copper heater core if it was made, as it would be the best non corrosive option with a copper water block.