I have a 1987 nuwa hitchhiker 27 ft. 5th wheel. It has a 8" sq. coupler box with a welded plate and king pin. I am getting a 2006 ram 2500 diesel mega cab with 6 ft. bed. I want to get a sidewinder hitch so I can use the camper with this new truck and not hit my cab. all I see are 12" turrents. how can I make this work with this 8" welded box. thanks for your help, outbound.