I'm at the same point on my '36 bed. It may take awhile to find the right stuff, but in the meantime I'm going to use 8.5" hex head bolts at the four corners just to keep the project moving forward. It will be easy to take them out and slip new ones into place once the correct ones are located.
Until the bed is mounted, I can't finish the gas filler neck, tail lights, rear fenders, running boards, etc etc. So...doing what I can to keep moving forward.
I have a tendancy to get hung up on doing something 'right' and it puts roadblocks in the project. I think its like what they refer to as 'analysis paralysis'...afraid to make the wrong decision, so no decision gets made. I almost gave up on getting door handles and window cranks because I wanted the best ones. Well, finally decided SOMETHING is better than NOTHING, and if I spent $40 bucks on handles I don't like, worst case scenario is I take 10 minutes and swap them out in the future and then re-sell the ones I'm not using.