"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).
Increasing chamber cc's reduces the compression ratio. If this "builder" is telling you otherwise, run do not walk away.
The simple solution is to pick a compression ratio and then find a piston with a reverse dome/dish volume that will deliver that number at zero deck with your chamber CC and .039" head gasket.
Like MR_P_BODY said, if you can't find a shelf piston, a $35 upcharge gets you exactly what you need.
I don't know if 440Source is still a Ross dealer but Ross did up a 34cc reverse dome for my 4.15 493 Source kit that became a shelf stock item until Brandon changed suppliers. I was looking for no more than 9:1 for 87 regular gas and a 34cc dish put me at 8.97:1 with zero deck with RPM heads.
Kevin
