Hi King

Here is something recommended by forchetto, which has proven to be very useful.

If the bolts go through the holes and are tightened against a nut, I'd recommend the use of a spring washer under the bolt's head and a normal washer under the nut - but use a locknut. All this if spaces allows.
Important: locknuts have to be replaced by new ones once removed.

If the bolts go into a thread, I'd use a spring washer under the bolt's head and Loctite the thread. Be careful to use the right Loctite. There is link in forchetto's post, leading to a Loctite write-up.

Bolt quality should be 8.8, best for vehicle use I was told. Lower grades may be too weak, higher ones too brittle. Our company e.g., instructs for replacement of 10.9 and higher grade bolts and nuts after they have been removed once.

Andy