I would buy they from the dealer as they are likely metric 10.9 shouldered bolts. This won't be expensive and it is the safest solution. If you MUST use hardware bolts, get 10.9 or harder (NOT 8.8), make sure they are NOT too long, DO NOT use a lock washer, a flat washer will be fine, and use red or blue lock-tite. Then turn the engine by hand to see if the heads of the bolts protrude out too far and hit on the engine or a shield or whatever. I still would recommend the dealer for this one. Sorry.