after destroying my motor i had dart short block assy shipped in . after looking at the lifter area of the new block i noticed that the block has a machined area cut diagonal to the lifter bore's . am i correct in guessing this is to accomadate roller rocker assy tie bar. ?? NOW HERE IS MY PROBLEM i have an old isky blower cam and flat tappet assy that i was going to use. the lifter's measure to be appr. .842 but the lifter bore's in the block averege about .836 or so. ?? is there a difference in the diamater of a flat tappet vs a roller lifter ?? or did they forget to do a final hone on the lifter bore's ???