I ground my factory block for roller lifters had no problem there.
Factory block isnt an issue running roller lifters. Many just drop in. Same with X block. Just drop in 59 degree R3 blocks are different in the lifter valley area than all others
69 Dart GTS A4 Silver All steel, flat factory hood, 3360race weight 418 BPE factory replacement headed stroker, 565 lift solid cam Best so far, low 10.30’s 1/4 1.41 best 60 foot 6.56 at 104.17
