340 compression ratio

Welcome Steve. I'll try to digest your post, but the easiest way to get some idea of compression would be a simple Compression test. The heads you have would be around 70/72cc in stock form and have 1.88 int valves, but they could have been milled and different valves installed? That's a pretty stout intake also. A vacuum reading at idle from a port at the base of the carb can also help reveal how mild/radical the cam is. I'll reread and see if there's any other info i can add.

Also, do you know what trans (904/727), torque converter (stall speed) and rear gear you have?