Hello from Colorado: No shrimp boats here. We do have lots of snow in the winter months, usually.
Trigger warning: Airstream trailers are built from aluminum. Aluminum is an excellent conductor of heat. The walls are 1 1/2 thick. Airstreams are harder to heat in the winter and harder to cool in the summer. Improved insulation helps some. Many folks full time in an Airstream. I'm just saying there are rigs designed for full time living and Airstream wouldn't be in that category.
The Airstream trailer is built as a semi-monocoque structure. It has a light weight flimsy frame, a light weight aluminum body, and a plywood subfloor all sandwiched together to become a strong unit. Loose anyone of the three, the structure becomes weaker. The bulkhead walls add very little strength to the trailer. Heck, the bulkhead walls are typically made from 1/4" plywood. If you intend to renovate an Airstream, make sure the frame, subfloor and body are sound.
The best way to check the subfloor is with an ice pick around the important perimeter of the trailer. Follow the interior walls and poke with the ice pick. I found several spots at the rear of my 75 Overlander where the ice pick fell right through. And stand on the rear bumper and push down with your legs. Look for any gap opening up between body and frame. If you see one, the trailer has "rear end separation" likely due to subfloor rot at the rear. My Overlander 27' had a mild case of it.
The specs for vintage Airstreams are listed in the Airstream archives found on the Airstream Inc website. Here is the link:
I'm guessing the 81 trailer has about a 50 gallon fresh tank, and about a 30 gallon gray tank, and about a 30 gallon black tank. I might add a mid bath trailer layout is better in my view than the rear bath like my Overlander. That way visitors can get to the bathroom without walking through the bedroom.
I would expect an 81 Excella to weight maybe 5800 pounds dry. The gross trailer weight is the maximum the trailer can weigh ready for the road. That is all the tires, axles and frame can carry. Don't be planning on installing a hot tub in an Airstream.
Ducted AC units didn't start until about 8 years ago. Vintage trailers have old fashioned RV air conditioners roaring on the ceiling. Newer Airstreams have two AC units and a 50 amp service to power them. That might be a consideration if you see very many hot, humid spells in your area.
I hope I helped you a little bit. I think others will join in and offer more information than I have. You will find folks on these Forums to be very helpful.