I found this on a Ford chat. It is a couple of years old but I doubt that it has changed much:
The 57.8 ft. (Curb-to-Curb) and 59.7ft. (Wall-to-Wall) is exclusive to the 176" SRW and DRW; this is the 8' box.
Shelby says:
The 53.0 ft (Curb-to-Curb) and 54.9 ft. (Wall-to-Wall) is unique to the 160" WB; this is the 6.75' box.
Shelby says:
Is there anything else I can help you with?
Bill says:
OK. since you asked... F450 pickup turning circle?
Shelby says:
The F-450 Pickup is unique to DRW and the 176" WB. This model has a turning diameter of 50.4 ft. (Curb-to-Curb) and 52.5 ft. (Wall-to-Wall).
So the 450 (only available in long bed) has a 2.4ft smaller turning circle than the short bed 350.