Gotta be a trick to this.
Yep... and here's the trick:
The part that is spinning, the trunnion, has a slot on the outside of it. With the tail gate closed you will see a hole in the bottom of the tailgate that lines up with the trunnion slot. Again, with the tailgate closed, stick a scewdriver in the hole in the tail gate, and into the slot in the trunnion. This will prevent the trunnion from rotating while you remove the bolt.
That's how it worked on my '65. Of course mine is a high plains Colorado truck, where it's dry.. not much rust here.
Hope that helps.
