I'd say that depends on what internals this engine has and what the most efficient speed is for the propeller. If it is designed to run at 3,000RPM you are pretty good already. If the engine is bone stock you don't want to run it continuously above probably 3,200RPM anyways. If it has a different cam/crank/pistons/etc. then you'd want the carb to match.

Your current build is somewhat restricted by the 2-barrel intake manifold.