I have a couple questions about cylinder heads, parts, and machining, first, here is my combo:

Late model (72-75) 455 8.5:1 engine with Stage 1 valves and upgraded HD valve train (stamped rockers) Cloyes double roller set, Sig Erson cam (.504 lift, 235/245 duration @.05, 108 degree lobe separation) TA Performance single plane intake, Edelbrock 750 carb, exhaust manifolds into dual 3" exhaust, 3.42 gears.

I'm looking to gain a little compression so the cam plays nice and hoping to do it without pulling the engine -

I have a pair of '71 closed chamber (661 casting) heads with cast aluminum rockers, I'm thinking about having them milled .020 under stock to gain a little in compression without having to buy new pushrods.

*** My machinist can't find the information - can anyone tell me where to measure these heads and what the measurement is to see if they have already been milled? ***

As for the rockers, my main concern is reliability, should I stick with the stamped steel rockers (they are almost new) or check the aluminum rockers for cracks and run them? They do show a little wear at the tips.

Any information will be greatly appreciated.

Thanks!

- Steve