A kingpin adapter is provided having an upper wall and a lower wall that are affixed to each other through side walls. The upper and lower walls have a kingpin aperture and a hitch ball aperture that is spaced from and parallel to the kingpin aperture. The kingpin aperture receives a kingpin and the adapter is affixed to the kingpin using pins that extend through the side walls and extend through a portion of the undercut in the kingpin. The upper wall has jack screws that extend through to contact a skid plate that is affixed to the kingpin. The jack screws affix optional adjustable fences that rotationally constrain the skid plate by contacting lateral edges of it.