Please help me diagnose this 273

First thought was vacuum leak, then I read the results of the compression test. IIRC there should be no more than 20% variation from lowest to highest, you have 50%. Valve adjustment may help or even resolve it, assuming the possibility of carbon buildup, but I would expect at the very least the heads need to be rebuilt, burned seats or valves is my bet. Agree with Oldmanmopar on the timing chain, seen it many times on small block Fords.
Good luck and keep us informed.