My dad had one when I was a kid. It was a 2WD 3/4 ton with a 350 and a 3 on the tree. He bought it from someone who was selling of their fleet.
They had toolboxes that fit the bedsides after the fenders were removed. When the trucks wore out, they sold them with the unused fenders in the bed and moved the toolboxes to the new trucks. Unfortunately for Dad, he didn't notice that his had one Chevy and one Ford fender in the back.
I saw one for sale locally a couple of years ago. It was the same setup as my Dad's, but a different color. I would like to have had it.
Slonaker