the PAW cam I recommended requires a spring with seat pressure of 100 lbs. and open pressure of 265 lbs. I have used it with stock valve springs. If you decide to use the Summit cam #6400 then make sure you have the high stall torque converter(fat ring gear). The PAW cam is rated 1500-4000 RPM. The Summit cam #6400 is 2000-4500 RPM. I guess the choice depends on what RPM range you do most of your driving