"Give Ron Beaubien at Diamond Pistons a call."

Tried calling him a couple of days ago and apparently he doesn't return voice mails as I never heard back from him.

Another suggestion that had come up is to increase the heads cc's to 92 in order to increase the compression. I'm not sure I would want to do this (or milling for that matter) in the event I ever wanted to use the heads on another motor. I'm thinking of going back to my original plan of building a 470 and using the RPM heads as-is with flat tops to avoid having to alter the heads in any way (other than porting).