im thinking about going to a NSA roller rocker. i currently have the self aligning cranes and was wandering if i need to go to the NSA for my rpm range. if not ill keep what i got. also would it be better if i get the comp r lifters? i hate to change all of this over but if i need to i will. also if so how hard is it to change the rocker arm studs and can it be done with the heads on the car?