It looks like there is 3 sets of rails. The unpainted bed rails. Then there is the black rails that are pined to them. Next set of rails are the cross rails that the hitch is pined to. These are bolted to the black rails just below them.
I verified that the under bed super rails are in the correct place. The hitch has the king pin setup directly over the rear axle.
Not sure if i need all 3 sets of rails above the bed. I have zero experience with 5th wheel hitches.