A 450 running 7600 RPM is about the same as a 500 running 6800 RPM. I know it could be done but it would be very expensive. Think about the heads an average guy could afford to turn a 500 7500 rpm and still make power, not a bucks down guy, then what I said becomes very clear. Not a lot of cross section available with any readily available head that is even remotely afordable