Welcome bwchant. We both have old 1966
Airstreams, yours the top of the line Sovereign
30 footer, mine the smaller base model Trade Wind 24 footer.
These Air Forums are a great place to garner ideas for your renovation project. I'd like to lead you to the Airstream Knowledge base and then Travel Trailers toward the bottom of the home page. Here you click on Sovereign
, and then click on the 1966
year range. You will meet folks that have restored and renovated their trailers. You will likely find some pretty novel interior layouts that might work for you.
One of my favorite refurbishment threads is "little girl refurb". These folks did a great job doing what you want to do. They completely redesigned the interior of their trailer after it was rebuilt and made sound. Take a look...
BUT... It sounds like your old Airstream has been neglected and abused through the years like many of them. Maybe you have tried to assess it's "bones" and determine what is needed. Most old trailers need axles and brakes, most old trailers need subfloor replacement or repair, most old trailers need new plumbing and electrical systems, most old trailers leak rain water like a sieve, and most old trailers need new appliances like furnaces, water heaters, fridge, etc. These need addressed before you need to start on the interior design and rebuild or polishing the exterior skins.
I remodeled the rear bath area in my 66 Trade Wind after replacing the subfloor back there. It was my first attempt at "Airstream interior design". I admire how Airstream designers make so much stuff work in such a small place. It took me several tries before I got vanity, toilet, shower stall, closet, medicine cabinet, drain lines, electrical outlets to fit and work together. I found the design phase challenging and creative and fun, but not easy for a novice like me. Building it was even more of a challenge. My new bath works, but it ain't gonna win any awards!
Again, welcome, ask questions, learn to use this excellent website, post some pictures, and have fun!