Milling the heads will definitely help and some porting really helps. The pushrod pinch can be opened up a lot on the intake ports to really help flow!

Clay your valve reliefs and see how close you are to the back side if the fly cuts but most TRW are fine with the 2.14 valve.

According to some most of us should not be offering advice unless we are Pro racers (I'm a hobbiest racer) or engine builders so sorry if i'm out of line. The 509 where it is degreed now will like the added pop even more!