As many as you desire EDIT I'd want to chase the threads w a "thread chasing" tap as opposed to a regular metal cutting tap, lightly wire brushing the bolt threads, making sure the bolts do not bottom, lube threads w 30 wt eng oil then blowin them off w shop air, multiple torque sequences, eyeball the bolt threads for any nicks/damage. #1 decks (head & block) milled flat, slight chamfer on deck bolt holes, a bit anal but that's me