67mustang302

I wouldn't even mess with a flat tappet these days, just not worth the hassle. You're limited on cam profile, because once you start turning higher rpm with large cams, the spring pressures required and the force generated starts to tear the lifters and cam lobes up, especially with modern oils. Hydraulic roller for 0 maintenence street use, for high rpm street and race, mechanical roller. Flat tappet is really only useful in class racing situations where it's required. A good mechanical roller setup will still require periodic valve lash checking/adjustment, but in a street car if you use good parts you shouldn't need to worry about much