Irrelevant, the old Super was a regular cab and you’re comparing it to a four door.
Ford did make four door cabs in the ‘70s too. I had one.
The point of the Super was how far rearward in the bed the axle was, and it was further rearward in the bed than any other pickup. It resulted in less rear overhang than any other.
Sure a 2018 crewcab will compare well... although that old Super probably had more payload!
Compare it to a new Ford regular cab, and though the new one does actally have one more inch of wheelbase, because the cab is bigger, the old Super will actually distribute the load of a long camper better.
It’s not superior in every way, but it did balance campers very well.