How long this engine has sat without a start up is completely unknown.
Thank you for the ideas! Today I will rig up a temporary way to run the engine for extended periods. I will perform your overfilled crankcase procedure as well. Perhaps ACDelco GM engine cylinder/combustion chamber cleaner will find its way into the engine as well. After a while of running and flushing the cooling system I will perform another compression test alongside performing a leak down. Lets see if I can't get to it before the rain falls.
Ill come back with an update
Side note - I've heard Valvoline VR1 Racing oil is preferred for our old blocks due to their zinc additives. Would anyone have anything to say for or against that oil choice? Thank you!