I'm fully aware that drooling over an SOB on this site is punishable by 30 days in the electric chair, but a 1978 GMC Birchaven with
4000 ORIGINAL miles (142 mi/yr!) is worth a look.......

http://cgi.ebay.com/ebaymotors/1978-GMC-BIRCHAVEN-23-VI...QQrdZ1QQcmdZViewItem

Looks exactly like the one I had, but mine had a rear bath, not rear bedroom. Same colors, too, but my upholstery pattern was more conservative.

It was a well-built unit, but I didn't like the handling. It was a tail-wagger, & dicey on interstate truck ruts. You had to maintain a twitchy balance along the edge of the rut, or it would throw you side-to-side.

There's an active GMC technical forum, & historically a lot of discussion about tail-wagging. My theory is that some of it results from the single rear wheels, & some from flexibility in the leading/trailing arms of the rear suspension.

I had another rig with single tires on the rear that was worse yet until I installed a panhard rod (track Bar) to eliminate lateral movement of the rear axle.

Low miles on them but the tires are 28 years old......first stop, the tire shop.