I noticed this one last week too. I suppose the "can't find another one for sale" was specific to:
"1977 f350 crew cab, 2wd, 351 motor"
I did a really quick US craigslist search just now and didn't find another 1977 f350 2wd 351 motor crew cab for sale either
BTW - Image 4 is of the motorhome off to the right in image 1.
The first time I looked at this ad I thought well yes, it is the only 2wd long bed crew cab that looks like this that I've ever seen with a doghouse in the interior like the dodge and ford vans and motorhomes had/have. Upon a closer look, I realized that the last pic of the interior is not from the crew cab.