Thanks for the suggestions Patrick. The less invasive I am the better.

The only access panel in the whole unit is a 4 X 4 inch panel at the top center of the tailgate. This panel allows access to the tail gate latch bars.

Due to the wood framing inside I can not see the entire inside of the assembly. That is why I decided to drill access holes at the bottom where I can later plug the holes with removeable plugs and then cover them with new weather stripping.

There were only 59 of these built in 1946 so finding another tail gate would be imposible.