Rebuilding engine/ head gasket compression question

you can gain a ton of HP with machining...factory tolerances were pretty wide, so everything is not neccasarily where it should be....deck heights, deck angle, line bore, cam bore, piston bores, lifter bores, etc.

They say Richard Petty gain 25 hp alone by properly align boring/honing the cam and crank bores in relation on the 426 hemi

stock pistons are not a great idea unless the motor is very early 70s or before because you will lose a large amount of compression