it's all about flow and chamber size. The chamber size will have the final say on your compression ratio, and the valve size will determine your flow. You want the two-oh-twos valves for max flow, and then some mild grinding to unshroud them ( but don't enlarge the chamber too much ). Pretty basic stuff. Get a 350 build book, there are plenty out there to choose from and they pretty much have all the same information, wheras the 350 is the most common motor to build.

Peronally, I haven't made the leap to aluminum heads yet, but I can see it in the distant future. Money on your heads is money well spent, provided the chamber size is right for what you want. The heads and cam gotta be matched up, else it will be a dog.