Help on 408 build

PRH said
The verification that the cranking compression is too high is the fact(from what’s being described) that it won’t even come close to running on pump gas, even with octane boost added.

Sure, double checking with another gage is fine....... but whatever the CR is...... it seems to be too high.

I’d plan on at least pulling one head for some measurements.

I agree as the heads will probably need pulled anyway for a gasket change. It’s been a long time since I’ve played with factory stuff. While the head is off I would lay a head gasket on the head to see how much chamber work (metal removal) is available to gain a few cc’s. Heck the head may even flow better and be more efficient.