Check out the Revcon camper. I think that it's been for sale before. Not affiliated with the saler.
http://inlandempire.craigslist.org/cto/2151795301.html
http://inlandempire.craigslist.org/cto/2151795301.html
4x4, they call it. But which four wheels?
It says it has a tag axle which usually means the very last axle is non driving and just there to hold weight. So that means the front axle and the front of the two rear axles are the driving axles. They took a regular 4x4 cab/chassis, lengthened the frame and added the very last axle, probably used a heavy duty trailer axle. It would be cool to make it into a true 6x6.