I looked at a 79 Ambassador last summer. I really liked the couch along the side, and fold up table under the front window, and a recliner on the curb side. The one I looked at was a rear bath, twin bed. The Airstream archive literature you attached would indicate a late 70s model.
This particular 79 was an International. But man, it sure had delamination and warpage of the interior cabinets. The overhead locker bottoms were all warped. I was very disappointed in the plastic "formica" (melamine I now believe) that had delaminated from the wood. My 75 Overlander does not have delamination issues. This trailer also had a significant case of rear end separation as well as other needs. It was a project for sure. I decided to pass on it.
Ambassadors are kinda rare I think. Maybe folks just went with the Sovereign
instead. I don't see a lot of them in the Classifieds.
Good luck in your search.