I have an 80 and a 82 and they both have fiber optics. Don't pull the switches! You'll probably crack the finish on the wood dash panel, the bulb is under the AC panel as Jeremy said.

The water is probably leaking into your trunk through a small crack in your tail light under the trunk lid. This is where all the water is drains to. Caulk your tail lights.

The lights flashing slow intermittently is probably caused by dirt on one of your bulb terminals, if it were the relay, you'd have the same problem on both sides.