Question about EDELBROCK RPM heads

Which head exactly are you considering? The edelbrock #60779 has a "closed chamber" design. The 340 (68) has a piston that sticks above the deck surface by .018 thou. your head gasket choice may be a .039 thou thick (felpro 1008) choice. This is not enough clearance left between the top of the piston and the head. OR... Edelbrock #60179 has a recess of .060 for clearance built into the head (at 65cc chamber volume), so you can run pistons that stick out of the hole.