If you had forged pistons, I'd recommend a shot of nitrous to get you to the 500 hp mark. It is the least expensive way to do it. But since you have hypereutectic pistons, I would run it the way it is. You have to build a blower, turbo or nitrous engine from the ground up. Add-ons are definitely not the way to go in your case. Thin .060 overbored cylinder walls and hyper pistons are a recipe for disaster.