Grade 2-5-8 are strength ratings. Not the same thing.
Everyday bolts are made en mass on an automatic thread cutting machine... tolerance is very forgiving. These are NF-2 rated threads.
NF-3 rated threads are precision cut and have 0 tolerance.. that means the tolerance is +/- 0 (ie an EXACT fit).
The mounts are for a 1943 G506 1.5 ton truck.
I found the bolts but the are $6+ each +shipping. I'm just gonna drill/tap for 5/8-18NC and live with it that way.
