I'm not sure about the model number, but we had a Triad-Utrad "Univolt" in our 1980 Airstream. Our fuse panel was also separate from the charger.
We replaced ours with an Intellipower. Replacement is very straightforward. There are essentially only 4 wires to connect, two for 120 VAC input (well, OK, 3 wires if you count the safety ground) and two for the DC output, + and -.
In addition to taking better care of your battery you will find that a modern electronic converter will eliminate any annoying hum you used to hear from the old one, and save about 40 pounds, as the old one was a real boat anchor.