---Well I joked about 10 years ago and a couple times between that when one person's acts up, it's time to check others' (E.G., One's "Gold Box" fails and causes others' to, One's Rear Wheel Bearings start raking, another's follow suit).
---Right now I'm seeing a lot of threads related to bulkhead connectors and ammeters acting up. I would say check those first and then be sure you have good grounds. I gripe too much about how steel is an ineffective ground, so I just figure I am one of few that really care if power can complete it's cycle. Also, as stated, ignition switch would cause turn signals to go out as well.
---Fuse panel would be on the bulkhead/firewall. Pop the hood and look behind/under the brake master cylinder for the wiring harnesses that come out of the firewall, kinda between the parking brake and brake pedal IIRC. The other side of that will be your fuse panel, inside the cab.
---Fuse panel design was changed in 1979 to a big, bulky plastic connector, which in the back, is where the wiring harness plugs into from the outside. Same crappy design GM had on their vans if you ask me. Vans were well known to start on fire there too. Black dielectric grease like a tar is found inside there, between the terminals. Often times it gets hot, melts/drips/disperses/seeps in between terminals and prevents continuity. I would pull the fuse panel & connector, pull one terminal at a time and clean it and it's slot in the connector/block, then gently squeeze the knurled/rolled portion of the female terminals with a pair of lineman's pliers to snug them up, apply dielectric grease to all terminal slots, reinsert the terminal, making sure it locked in place, and after cleaning/adjusting/etc. each terminal slap it back together.
---Did the gauges fall or did the ammeter peg out to the Charging side? Did you have the heater on? They changed design on the heater controls no? Is the heater fuse getting hot? Will check the wiring diagrams on the 1980 and see if it's set up the same as the 1978- Scouts. A lot have, including mine (StoneThrower prior to rewire), had issues with the what... #14 circuit(? ) melting the insulation... Battery Feed Connector & Dash Instrument/Illumination Connector