1. Deck clearance or "quench height" is the distance from top of piston to surface of block. Stock is usually .020" - .030". Not to be confused with deck height. SBC is 9.025" deck height. Rod length (5.700") + compression height (1.563") + quench height (.022") + 1/2 stroke length (1.740") = Deck height (9.025") is typical of a Chevrolet 350 CI and a 4.3L V6 engine .
2. The composition head gaskets packages will have the compressed thickness listed. My Fel Pro gaskets are .041" compress thickness.
3. Effective dome volume is listed on the piston specifications when you buy them. It is a negative amount such as -13 CC and is subtracted from the chamber volume. Example: 64 CC combustion chamber volume - 13 CC piston head volume = 51 CC chamber volume. Since the elimination of leaded high octane pump gasoline, the domed piston in most street driven engines are a thing of the past. A SBC combustion chamber volume less than 64 CC is all that 93 octane pump gas can take.