John,
I'm assuming you're talking about the frame of the companion 5th wheel hitch as no part of the gooseneck protrudes into the bed. I can't measure from the front of the bed because I have a Weatherguard 5th wheel box mounted there, but from the back lip of the bed floor to the forwardmost edge of the companion 5th wheel hitch frame is 60" (5') exactly.
Rusty