I had a set of the Edelbrock RPM heads on a 501 in a car that I sold. They are expensive, but I believe it was the best money I spent on the build. Out of the box they worked great, next set I would like to get some port and flow work done and realize a bit more of their performance potential. As good as they worked, doubt I would ever go back to cast iron. With the price of parts, flow bench time, and porting work on the cast iron not sure I really would have saved that much using cast iron. The weight savings is considerable, also. The BBF's are such torque monsters anyway, I just bought the stroker kit, balanced the bottom end, bolted on the heads and intake, and used an MSD "plug and play" distributor. I have myself convinced the expense is justified. !!!!!!