360 piston id and compression test results

So what are you doing with this engine/car? The gears speak to higher CR and torque in some fashion. Even with the flat tops pistons, with your dimensions given for the piston top in the hole, give 8.1:1 Static CR with a .028" head gasket and stock J head chambers. But, really, you need to cc your chambers. I suspect the heads have been milled for you to get the cranking compression numbers you showed. And the 'tire boiling' backs that all up. Or it's a pretty short duration cam.

More HP is simply in head flow as said. Edelbrock Performers have the flow and the smaller chamber puts you up just under 9:1 SCR.