Never use the head gasket to increase chamber volume. That also increases quench, which tends to increase detonation and decrease efficiency. Use the head gasket to set the quench area as small as possible, regardless of your SCR and DCR.
DCR is more important than SCR. Be sure to calculate that. You might be able to improve DCR by changing the cam.
But, I think making a high compression iron motor survive on pump gas is going to be really difficult. Unless you live at 10,000'ASL.
If it were my car (and it's not) I would pull the motor down, replace cam, pistons, and heads to match what I wanted it to do. I have had a car with 12:1 compression and a huge cam; and that's what I did.