Main studs. The clamping force is different between studs and torque to yeild fasteners and can distort the main bores by a few thousandths if used directly in place. Line honing is necessary to correct itI'm pretty sure KevinM had some head lift on his stock block with stock bolts and his SVO. Not sure what getting the block line honed does. When I first got my ARP studs Rob installed them on an Explorer aluminum block. They were then transferred over to my BOSS block when Rob did the last engine swap. I've never had any experience with or without them on a stock block.