Getting the most power out of my 400 stage 6 heads

IQ52 said
A well worked Stage VI head at 68cc has probably been milled quite a bit, so the valves are going to be even closer to the pistons than with a stock head. You are going to have to put a cam in the engine and test the piston to valve clearance. Why not test the clearance with the existing 509 first, using the STG VI heads, and see what you have to work with? Bolt the valve train and everything up and measure the clearance. That's what we do at the shop. You have too many variables to say from here, "Yep, them pieces are gunna work!"

Well the 509 is what I pulled out the engine so I know it clears. I know once I buy a cam and get the pushrods and everything for it I'll of course bolt heads on, use some putty and check clearence on top of the Pistons I just want a ball park idea of what is enough to make the most power possible without it being too much because it would suck to spend a couple hundred bucks on a cam&lifter set then it not clear pistons and be Stuck with a cam I can't use nor return because it's been installed...