Welcome High Road: Let me see if I can get a discussion going on what you might be looking for. You mention a couple of key requirements like "full time", > 27', lots of sunlight.
I might suggest you look for the 34', triple axle Classic, or Limited models. They started making them in 1983 and pretty much stopped regular production in or around 2008. We have a 86 Limited. You can find a couple of floor layouts for these models, e.g. twin beds or a double bed. Check on the Airstream.com website, archived documents.
I suggest the 34 Limited, maybe even as late as 2000. There are many examples for sale. Many are in darn good shape. You can always decorate to your tastes. There are always things to fix or make better on an old Airstream. The extra room in the 34 is a blessing for full timers. I recommend a 3/4 ton tow truck for a more secure experience in the mountains.
We really enjoy ours. We have had it since 05. Picture below.
Airstreams are nice ovens in the hot sun. The aluminum exterior gets pretty warm. We find we pull the blinds to lessen heat ingress inside. If we want sunshine, we step outside. Airstreams are best in temperate climates. Minnesota winters aren't made for Airstreams, and neither are Texas summers. Be prepared to travel where the weather suits your Airstream.
There, you may now get 50 more recommendations better than mine.