Tailgate trunion bolt size?

[msg]

This is for a 1966 fleetside if it matters.

Once again I cant find the bolts I removed and I have got so many coats of paint on the bed panel that I am sure I will have to re thread the opening for the bolts that mount the trunion hinge to the panel. I think its 3/8”-16 x 1” course but before I tap it the wrong thread and buy the wrong bolts I hope someone might know. The part doesnt come with new bolts so I will be looking to buy stainless. The bolt in the pic was from the set of the hood hinge to hood bolts which were 3/8”-16 x 1” course. I tried using it for size but with the multi paint layers and all it wasnt threading easily.