casting material? cost?

best would be Magnum Edelbrock Aluminum heads, or something from Indy that's designed to use the pedistal rockers and oil through pushrods.

but those will also be expensive. The edelbrocks will support 500 crank hp out of the box, but will run you $1600

EQ heads are a good choice, and can be opened up with port work to make some serious power, but they are iron which weighs more and you'll have to pay attention to compression. a decent set of unported heads will run you $800, but as soon as you start porting, you're looking at $1500-2000.