main studs vs bolts

The cap, block, and fastener work together. The factory bolted the cap in place, and that bolt exerted a certain amount of holding force which distorted the cap a little. Then the main bore was cut and honed. The issue is when you change the fastener the amount of distortion changes too. Not to mention the studs sometimes do not fit the cap holes right and the holes need to be enlarged very slightly to get things to work. Plastigage is not a valid measuring method... It's better than nothing, but it's like setting the pointsw with a matchbook cover.... Yeah, it's better than nothing, but it's not that accurate. The way the bores distort is usually at the parting lines, where the bore get's tighter as the sides draw in. Platigage can't measure the clearance there. Also some bearings have more eccentricity and may not be a problem. The bottom line is unless you use a dial bore gage to measure the bores at three points, you may not see the change. But the bearing will. Bolts-forbolts may not change much. But studs preload the caps a bit more than any bolt, and much more evenly, so the distortion gets much worse.