Warner bodies does a bed for dodge md trucks. Some dealerships will have them on the lot with a bed, but they do not come from the factory with a bed, it's an aftermarket add on-
Warner Bodies
I think you'll find the f-450 with the bed is not really an f-450. Not completley sure of all the details, but I know right off that the 450s with a bed come with 17" tires not 19. 5" so to me that says that it's not built the same or intended to do the same work as a true C&C 450
Forrest
Afterburner is correct, the new F-450 pickup has been de-contented from the previous version. I believe its only current claim to fame is that it retains the wide front axle of the 450, enabling a greater steering angle and the corresponding tighter turning radius.