Let's face it; we are not about to run out of 1948-1955 Chevrolet truck cabs anytime soon. These trucks were produced in huge numbers, and due to their sound construction, many of them survive today.
There was a time when all sorts of creative, albeit unrefined, methods of rust repair (we use that word loosely) were to simply cover it up with fiberglass, a chunk of sheetmetal screwed into place, ...