I think you should call some head experts and get their opinion with the cam you are using. I have a friend with a 10:1 555 Musi motor. It came with the 360/370 cc Edelbrock/Musi ported 24 degree heads. He took them off and bought 335 AFR Heads because someone guaranteed him a better ET. He went to the track and lost a tenth on his short time and ran a tenth slower with the same MPH. It depends on cam and compression.