Jim the block is a megablock, the original block for this motor. Guess you are right, it may have shifted with use, especially with all the flex this thing has had. My biggest concern is I have fairly tight piston to head clearance as it is, and don't want to risk moving the crank up too much. I am at .046 with 6.965 steel h beams and about .001 oversize on piston to bore clearance with 4.500 pistons. I will have to call the shop tomorrow and see what they say. On the bearing bores, I was referring to the diameter without bearings installed. Looks to be about 2.940?