Looking at purchasing a 1966 Dodge Panel Van

Maybe I missed something, but why do think there's a S. Africa connection? In any event, it's possible it was built either as a design exercise & escaped the factory somehow or it's a limited production for something like the militsry.
I stumbled onto something like some years ago with a '66 Chevelle panel truck. The seller claimed they were built for the Air Force back then. Fortunately I had a friend that was in the Air Force at that time & he confirmed they did have a few. They were support vehicles for Fighter Wings at the time. Perhaps your truck had a similiar purpose??