These day just like in the old days spring pressure is not your friend they get real high with a big MM hemi Cam shaft at an inch lift. This were RB. set up is nice and you can also get to a spring if you break one with the head on the motor in the car quite easy The 426 Hemi in my Challenger ran the stock rockers but back in the early 70s you did not had much of a choice. One rocker never broke it just was not the weak link yet back then.