1970 Dodge Dart 318 upgrades

The early engines were but the head cc's you see are minimums as are the compression distances down the hole are for a minimum deck block
piston heights are usually correct but aftermarket builder pistons are "destroked" usually .015 to keep compression same with additional cu in form overbore- at least that's the excuse
bottom line you have to cc every head and measure every compression distance
BTW the other option for low end is a blower