[tll74]

Many factors involved when picking out pistons.
1. cubic inches of engine, the bigger the engine the more compression with the same combustion chamber.
2. combustion chamber size.
3. deck height of block compared to piston height.
4. head gasket thickness.
5. cast, hyperutics, or forged.
6. iron or aluminum heads
7. how money you can spend without your wife or girl freind knowing about!!

Your Vortec head has 64cc chambers.
The most over looked thing in common everyday engine building is not checking the deck height of the piston. Nearly all pistons are destoked. Ive seen pistons on sbc's be as low as .060 down in the hole. This is a compression killer. I believe most, if not all, compression advertized spec's are based on zero deck height and a .038 head gasket. I find that 9.2:1 to 9.3:1 with a carb is max and that is with a very finely tuned engine. A heavy truck doing lots of hauling or towing will like a lower compression than a lighter truck running empty. Gear ratio can also can be a factor. I would deck the block to near zero to obtain .040-.045 "qench". Cast and hyperutic pistons work fine for stock to mild street engines.

These factors should help you figure out the best piston for your application.