I bought a Ford Bronco and I want to give it a little boost. So i pulled the heads and worked them over and while ive got it apart i want to put a different cam in it. I want a comp my dad has had really good luck with these. I went to thier website and they list hydralic flat tappet and hydralic roller??? What is the difference and what type was the factory one because i would like to go back with the same style because from the sound of it i would have to change to a different lifter or something to that effect. any help would be nice.