I was wondering why I see many people switch to ported 03 heads rather than ported FR500's. It was my understanding that the FR500's out flowed all the other 4 valve heads out there except the Ford GT heads. The reason I bring it up is that I'm thinking of doing a conversion soon and was looking at the FR500's. But some people are switching to 03's. For instance Nazman swapped his ported FR500's for ported 04's. Should I be looking at used 03 heads instead?