An adaptor for securing a fifth wheel hitch to the bed of a towing vehicle is described. The fifth wheel hitch is typically part of a larger assembly having attachment lugs configured to be removably secured to receptacles in mounting rails permanently attached to the bed of the towing vehicle. Newer towing vehicles are provided with recessed sockets in the vehicle bed, rather than permanently mounted rails, to eliminate obstructions to placement of cargo in the bed. The present invention is, therefore, an adaptor for securing existing fifth wheel assemblies to these newer towing vehicles.