[Marshy]

You might want to ask him what the quench distance is and if you can run a thinner head gasket to gain a little more compression with those larger style heads. I recently ditched my 0.040" thick head gaskets (FelPro 7733PT2) for a thinner 0.015" gasket (FelPro 1094). The change in thickness and diameter of the fire ring reduced the combustion chamber by 5cc and gained a half a point of static compression. I figured it went from 9.1:1 to 9.6:1, and runs fine on regular octane still. It could be more or less for you depending on your cylinder volume, don't assume you'll gain half a point in compression too, you need to run the numbers.