Hey. Sounds like a great plan! I spend 6 months of the year in my
Bigfoot. Compared with more egg-shape
fiberglass trailers, you'll really appreciate the extra space in the
Bigfoot.
I don't know about 1981, but here's the brochure for my 1991. The white column is the 17' model, though the capacities seem to be the same for all sizes (13.5, 17 and 19).
The tanks have sensors attached at different levels. If they worked, then stopped working, I'd check the ground first. If I knew where the ground was that would be really helpful to you...Honestly I'm not sure if these will have their own ground, or if there's only one ground for the entire
electrical system.
There's definitely going to be some corrosion. I think the sensors thread into the tanks. If you can remove them and clean them up, that will help. But I'd check for an obvious problem with wires and the ground first.