relocated battery and grounding kit ?
never had a problem with a seatbelt bolts. its about the only spot you are going through several inches of steel.
i am with mcor, i like to drill hole thru a piece of steel, that is accesable from both sides, grind paint/undercoating from both sides, use a star washer and bolt nut and lock washer, if it is a system pulling stupid power, i will tack weld on both sides, after i do all my grounds i still check resistance to battery!