I thought this process thru/When I was building a frame for a 78 4x4.
I concentrated more on the shoulder of the bolt being long enough.
I did not want to use a Full threaded bolt
I wanted the shoulder to be in full contact with the frame and the bracket it was going thru.
I used Hardened washers to take up the space / (If Any) then a stover / toplock nut.
Loctite on this would be a plus.
Hope this helps.