360 compression and cam questions

A couple of points. Did you actually cc the heads? Most J heads are over 70 cc's. Also, the bore on a typical Fel-Pro head gasket is 4.180" which lowers the compression. Unless you have accounted for all those dimensions you compression is more like 9.5 to one.

In any case you should be able to operate at 10:1. I amy running 10.6:1 in my 360 but with magnum heads which are much more detonation resistant and it runs on 89 octane.