You dont make the bores any bigger than the required specs, which have a low and high limit. The reason the bores arent " expanded" is because tyhe first thing you do is cut a few thousands of an inch off the feet of the main caps. The makes the bore " smaller" to start with, then you bore or hone ( two completely different things) back to the spec size. I prefer to hone to the low limit, which gives the maximum " crush" on the bearing shells. The bearings shells ( outer) dont change, they are all the same size. If a shop does the job RIGHT, they take minimal material off of the block sides ( saddles if you will)of the mains, so as to not change the crank to cam centerline very much. If someone doesnt do it this way, they then change that dimension, and if its been done several times wrong, thats where your " minus" timing chains come into play.