You can open the top of the ports to modify the port timing and move up the RPM of your power band. Getting your port timing identical on both cylinders is the most useful tweaks. I am out of them but there were 0.001" shim gaskets used to match intake port timing in addition to the thicker Cuyuna base gaskets used. On the 440 you really want to avoid more than 150 psi compression and then premium pump gas is marginal to use. I built one 2F440-3 with a little port timing and transfer port work that had 175 lbs compression with 4 bolt heads. With race-premium 100 octane mix it was a question of whether I finished a run before the head gasket blew on about the 4th set of head gaskets I burned a hole through the center of the PTO piston :'(