Grade 8 bolts weren't used in 1930's cars at the most grade 5 but mostly grade 2.
Yeah, sorry I should have mentioned, the truck is not factory original, it's been restored/modified at least once (and I'm in the process of doing it over myself!). Whoever did the work on it before me put grade 8 bolts in EVERYTHING. Everything from the timing cover, to the license plate holder. EVERYTHING has grade 8, kinda neat :)
I'm hoping these aren't cheap import bolts, because they look so neat. 95% of the other bolts have the standard 6 mark pattern on them that I'm used to seeing.