This is not an underpowered motor. Making 420rwhp N/A with a 4.6. That is impressive, great motor if you want that power just get nitrous or get a C16 tune with an aggressive high compression build and you will make some nice power not 500 but still nice.
PROCHARGER P1SC<WHIPPLE 3.4L
5.0 Stroker Built and Blown
Check out my build thread in 2005+ Talk