Airstream experimented with rear beds in the 1950's on several models and then basically abandoned them in the 1960's.
Rear beds first reappered in the 1969-1971 timeframe (I am not totally certain on the dates) in the 17'-23' models were they appear to be a somewhat rarer option to the usual rear bath. In these cases the bed was a rear corner bed on the curbside with the rear bath stuffed in on the street side. As far as I know after 1971 or so rear beds did not appear on any Airsteams 23' and shorter until the late 90's.
As for 25' models, I beleive it is correct that up until 1985 they were all rear bath models. The first time they had a rear bed was in 1985 - first as either a rear corner bed on the street side, or rear twins. Later this changed to rear queen or rear twins. As far as I know all 25' Airstreams since 1985 have been rear bed models until the 2005 Front Bedroom model came out.
Most all 27' models were rear bath except for a few rare rear bed models in the mid 70's (about 1974-76?). Rear baths continued until the 27' model was discontinued in the late 80's. When a 27' model reappeared in the late 90's it was a rear bed model.
As far as I know most 70's 29' models were rear bath, but from about 1973 on a rear bed was a rarer option. Then starting in 1984 all 29' Airstreams were rear bed.
From about 1973 thru at least the early 90's, 31' models could be have a either rear bed or rear bath. I'd guess that rear bath was more popular until the mid 80's, with rear bed more popular after that point.
Both the 32' and 34' models that were first introduced in the early to mid 80's have been mostly rear bed, but a few rear bath models do exist at least into the early 90's.
I think for the 29'-34' models from the 80's onward, the options were mainly rear queen or twins, but there may have been a few rear corner doubles thrown in in the early years.
I should add that Airstream made some 28' models in the 90's that were rear bed. There weren't many years that Airstream made a 28' models between the 60's (when they were popular) and the 90's. For the few years that they did (early 80's?) I have no idea what the layout was, because they are so rare I have never even seen pictures of one.
Wally Byam Caravan Club International Historian
Vintage Airstream Club Historian