"Factory roller motors will usually have two or three bosses down the webbing rib above the cam in the lifter valley for the lifter hold down plate. The tops of the lifter bores are machined flat instead of having a little 'crown' and the face of the block is clearanced for the roller timing gear."
some of the pre-roller blocks were built that way too (around 87-88) so the lifter bore "problem" isn't a problem...
