8) i wouldnt recommend using grade 8 hardware on exhaust system bolts, they are too brittle for that. you want a bolt that will expand and contract with the ehxaust, and a grade 5 bolt is better at doing that. i would recommend using factory style bolts instead, as indicated npd has them as does autokrafters. a better idea is to use brass studs and nuts for the exhaust, that way they dont rust in place.