This will not set well with some...but I have seen machine work performed on blocks by a CNC operated by a fairly well known place here in Ca. that was pure $hit! Just because it's on a CNC doesn't mean squat. You have to choose someone who knows how to machine what you want done. Having said that, if done properly, yes the lifters will be where the factory blueprints say they should be. You'll need to supply the lifters you plan on using so they can be measured to fit the bushings being installed. Less leak, possibly better or more accurate cam timing due to proper lifter placement, which can help the lifters (both flat tappet and roller) live longer.