Neat concept, but $$$. I think it runs about $12,000 now plus options. You should be able to buy a decent 4500 cab/chassis for under $20,000. It may have more miles, but the chassis and powertain are built for that. It's actually the cabs that wear out first (drivers seat first, then you start getting squeaks and rattles).
I've considered one on the past, but my biggest concern is traction off-road. You're moving the pin-weight off the drive-wheels, and adding even more total weight. Not a good combo for dirt and gravel IMO.
