[Spridgets] Top frame bolts

[Brad Fornal]

I just purchased another rolling 68 shell for a couple hundred bucks. I am
trying to get it somewhat water resistant, before the rains from Gustov hit.
I want to put the top frame on, to hold up a tarp. Can anyone tell me the
bolt size for where the frame bolts down behind the B pillar? It appears to
be a 5/16 18, but I cannot get the bolts to go in easily. Before I go to
tapping the body with the wrong die, I just wanted to check.
Thanks,
Brad