Otto,
Just saying but if only for luggage, then why bother to put windows in it? Just get a regular panel...?? I think the concept of having more doors in the Suburban type conversions came later -- probably after they learned that the passenger van conversions like this one were awkward.
The ones like this I remember seeing also had racks on the roof for luggage and skies, etc.
Another thought -- Maybe this had been an ambulance?
My van, although far newer, was originally spec'd and purchased as an oil field crew van.
Cool truck! Cool discussion!