Dont change the gasket.
Polish the pistons and chambers to allow for a little better cr. It will also help with knocking. They do not need to look like mirrors just knock down all the sharp edges. Should be able to take a few cc out without much cutting. But in your case i think your good if you run good gas in it.
I only run exxon 93 or sunco 94 in my performance cars. You just cant stop at the elcheapo gas and fill up with What they claim is 91. That even goes for new mustangs or corvettes. They will not be happy on crappy gas and gas station owners are not to be trusted. Not even a little. Lol