Tow dollies like Kevin has posted are not legal in a number of states. Only commercial trucks can use tow dollies for 5th wheels. If you plan on using one, make certain you'll be able to use it in the states you want to camp.
Here's a thread that you may want to read before making the investment of this type: http://www.fiberglassrv.com/forums/f...rig-30789.html
there's also information provided when Scamp
was contacted about a "Franken Hitch."