John,you not only have to clearance the block but you have to take into account that the lifter bore is .400 taller than a stock block,so you have to get a taller lifter or grind the top of the bore down so a conventional lifter will fit. These R3 blocks where designed from the beginning to be 48* and where cast with 6 bolts around each cylinder. They where converted to 59* as an afterthought, the lifter bore was moved closer in to the block to be 59* and the extra bolt bosses around the cylinders where milled off. What you have to watch for is that there are water passages running through the unused bolt bosses that you have to clearance for the lifter tie bars. What I did was used the rivet on the tie bar as my clearance point and I hand fit each lifter allowing a couple of thousands behind the rivet. If you just go in there hog wild with a grinder or Bridgeport you will hit water. Make sure you attach a piece of wood or something to the deck surface, it is very easy for the grinder to jump out of the valley near the top and nick the deck.-Randy