Re: My motorbicycle life story ( missed out some)
It's overkill in the sense that even a grade 5 bolt is FAR stronger than the engine case. You will pull out the threads long before you break a grade 5 bolt, much less a grade 8.
But it really doesn't matter much as either will work fine.
If more is better, then too much is just enough.
If you can't afford it, build it yourself.