I don't know if you have ridden in modified Z cars, but 240Z's are LIGHT. 320 to the wheels it's basically a widow maker. Overkill on power is overkill on power. You reach a point where more power is useless, as you can't put it down, and the car is already dangerous as-is. It's a street car. With the power level you are talking about, additional bracing is necessary in the subframe and rails. Do you like reliability? Stock=reliability, modifying it for 40-50 horsepower could take away the reliability. stock 370Z engine is fine power wise bone stock for a 240Z. A lot of the modern cars with all the horsepwoer....that's in a car that weights OVER 4000 pounds. 2 tons. Completely different deal. Your weight is about half of those. Be sensible. Live Longer. And this setup....stock brakes are NOT good enough, nor is a stock suspension.