Welcome aboard. The only practical way to get to 300+ with your engine is forced induction. In the U.S. no one really bothers with these engines much because of the lack of aftermarket support, opting instead to use dohc vtec motors for modification.
But even the case of these more powerful motors, 350 hp is achieved via superchargers or turbocharging unless you are a naturally aspirated maniac willing to spend big dollars and time, something that would definitely get in the way of your show-car priorities.