Hi there. We both have 1966
Airstreams, and both have plumbing problems. It sounds like you are embarking down the slippery slope of a bath remodel. I liked the way Airstream designed the bathroom in these old trailers with the fancy fiberglass parts and the hidden "console" toilet with a seat cushion on top. But my trailer had a rotted subfloor under the toilet, so I had to remove the bathroom to gain access to the subfloor. I had to replace the old copper plumbing. The black water tank was shot and I wanted a gray water tank to boot. One things begets another begets another.
So I cut the copper, and I cut the ABS drain piping. I removed the sink, bathtub, and toilet. And the project was under way. A year later I have it all back together and functioning again, but not as a "restored" 1966
So it is decision time. Removing old copper plumbing and restoring old faucets is a real challenge. Demolition with the intent to renew is a different approach. It is always best to save as many parts as possible, but sometimes it just isn't worth the time.
Here is what the original bathroom looked like, and here it is now.