Chris, welcome.
I have a 350, and will be installing my fourth radiatior in a few weeks. if you have a lot of aluminum parts, and this includes ANYTHING aluminum, all it does is suck heat right out of the block, and vwahla, at the outer area of the block is the coolant running through picking up all the heat. this heat jumps right into the coolant, and your radiatior had better be ready for the extra load.
I will definately go aluminum. I have the electric fan, and a mechanical fan, and I still run 195+. I suppose a GOOD standard type radiatior would do, but ive heard great things about aluminum.
also, i had a radiator rodded out and they told me that it probably wasnt a big enough radiator to begin with. i was bent on the cheap fix. I tried, I cried. that was #2.
a buddy has a nova and can cool his block fine with the stock v-6 core. same set up as me. (well, almost. something makes his crap painfully slower than mine

) just joking KIRK!
g