So, I've done the brakes, the fluids, the hoses, the carburetor, and removed all traces of the plow setup.
I finally got to pull the front seat and carpet to see how bad the floor was, since it has been up in New England as a plow-truck for close to twenty years.
Surprisingly, the floors are solid! There is surface rust on the driver's side, but initial scraping does not reveal any serious rust-through.
The passenger-side is amazing for this area.
There is a crack in the rear floor behind the driver's-seat that I'll have to weld up, but it doesn't need full floor-replacements like all the others I looked at before this one.
There was an amp mounted under the passenger-side seat, fed by an unfused 6-gauge cable coming through a hole in the firewall without a grommet. I have no idea if I'm going to keep it, but I'm not going to keep it there, given how much space there is under the dash on the passenger-side without an A/C unit, but at least it's disconnected for now.
The seat is intact, but not great. I'd replace it with buckets and a center armrest if one came up, but for now, I'll just lube the tracks, clean the upholstery, and reinstall it. I think it has been recovered, but it does sag badly on the driver's-side.
I'm not sure if I can save the carpet, which smells of mouse-piss. I will try shampooing it, but a replacement might be necessary.
I'm very pleased.