tighter quench would allow more compresison, I would run a thinner head gasket and try to get about .035 and it should need less octane in my experience. I have run more cylinder pressure than that on iron heads so you should be fine.

Part of the reason for quench having an actual clearance distance is to acount for piston rock so you can run it closer for sure. I have never had a problem setting em up with .035 clearance as measured from the center of the piston sitting flat in the bore.