Hi tmeagle1. I have a little information, enough to really mess you up. I replaced the fuse box in my 66 Trade Wind. I can not remember when Airstream went to "univolt" where everything ran on 12v
except the AC and the 115v AC outlets for the toaster, etc. My 66 is a univolt trailer.
One thing I learned is the converter powers the 12v
circuits in the trailer when you are connected to shore power, and the battery runs the 12v
circuits when you are not. The converter charges the battery when plugged in to shore power. So it is "EITHER converter OR battery". The converter pushes 13.5 volts at the battery preventing the 12.8 volts of the battery from powering the 12v circuits.
Here is the electrical diagram for my 66 Trade Wind taken from the owners manual. At least it shows the relationship between the converter and the battery. There are 3 12v circuits in my Airstream. You can see them radiating from the old fuse panel photo as three black wires. The white wires are connected to the "ground buss", which is connected to the frame of the trailer.
The Airstream battery gets charged by the converter as mentioned above, or it can get charged by the tow vehicle when towing. Handy. So there is a blue wire that comes into the fuse box that connects to the 12v plus side.
Airstream liked to use fuses and 12v circuit breakers. I don't know why the "belts and suspenders" design. I installed my new fuse panel without the 12v circuit breakers. Maybe I'll regret that some day.
Since some of the 12v loads are rather high amps, Airstream uses 12 gage wire. It's harder to work with, and harder to jam into a fuse box. 12v DC isn't much power to drive a furnace fan or a water pump. So you need bigger wire to push some amps to the job.
I also included a picture of my old fuse box, and my new one. I used 20 amp fuses on each of the three 12v circuits. You can see all the white wires jammed into the grounding buss at the top of the fuse panel.
The basic thing is to study the wiring diagram and trace your wires so you know what each one does. Wire color convention was goofy back then.
Hope it helps. Others will surly log on and better answer your questions.