If compression is more then 10% between the PSI the engine needs to either be re ringed or bores need to be oversized. Compression can also be lost through valve leaking through the seats. In that case you need to remove the head(s) and either lap the valves or take them in to get the heads rebuilt. A blown head gasket will push combustion gases into either the cooling system or Oil drain back system. Check the cooling system with the rad cap off and if you see bubbling it's pushing gases into the system. My 302 had that problem last year and the engine would show it was over heating even when the engine was running at 160-175 degrees as Air will heat up more then liquid so the sensor was getting a false reading.

Just a few things to look at, hope this helps.