I just put a small hydraulic roller in my 273, that was ground by Bullet. I used Morel hydraulic roller lifters because the oil band is low enough on the lifter body that it doesn't come out of the lifter bore and dump the oil out on each stroke. My rockers will oil thru the shafts like normal, but if my machinist orders me some hollow push rods, it will be just fine and can't hurt.