and wondering if anybody here knows anything about it. I've been lurking around the site for a while now, since I began looking last fall for a square body 3+3 dually. I've discovered I have an irrational love of these old trucks; my wife thinks I'm crazy.

I believe that is a common problem on this forum. I have found this to be one of the best forums out there for the hobby and glad I found it.
This truck is from western Canada, a 1977 with a '80 front clip, stock 454, built 700r4. The fellow that owns it had used it to pull his merlin powered 1/2 ton for a number of years and now is selling both. It spends it winters parked in his shop. It was painted a number of years ago, rockers were replaced, dash is perfect, interior is in good shape. All in all a very clean truck.
Thanks for your time.