The ground of the distributor will not have any effect on cylinder compression .
Your compression numbers are very low,,,,across the board .
I believe that is where you need to give your attention .
If the cylinders are sealing,,(,rings and valves,),,,,then it should be camshaft timing related .
If it ran good before,,,,and now it doesn’t,,,,check your cam timing components .
I do need to run the test again, and use the oil check to verify if it's the pistons rings. The heads were rebuilt in 2021 by a engine building shop including the valves and installing hardened seats so I am pretty confident they are good.
I read that low compression numbers across the board are likely a symptom of bad valve timing via a stretched chain, as bad rings would likely yield more inconsistent numbers. I replace the gears and chain myself and have yet to run a compression test again.