Yeah. Except that I'd get a proper Ford step box, and the back half of a Jeep pickup, put the Jeep box on it and build a trailer from it.
Those aren't Jeep fenders. Those are aftermarket boxes built specifically for logging here in the PNW. They used to be a very common sight.
But they were found on Jeep pickups, which made me assume that was Jeep's design. Do you know who originated the design?
^^^ Pickup camper immediately above... Can't remember the make of the camper, but it's one that raises up to standing height when you're camping (not driving), and lowers back down when you're driving (not camping).
They were, and still are, simply called a logger's box. Some were made by the logging companies in house. There were also small companies like Rebco that cater to the logging industry that built them. They are still around to this day.