Thomas --Here's a couple of quick things I'd check:

1. Use volt meter to check if 6V is present when lights are turned on or brake pedal is depressed. I check for the 6V on the wire jumper terminal located in the trunk very close to the driver's side rear tail light. You'll note that this terminal has two or three wires that come from the cabin area---these are the 6V power wires (lights & brake for sure).
2. If 6V is present, then check condition of bulbs. Sometimes the bulb(s) filaments appear OK (visually) but they are not ---try installing new bulbs.
3. Are the two wires connected to brake master cylinder "brake switch" actually connected to the terminals. Are these switch terminals clean? Sometimes one or both of these wires will loosen and come off the terminal in which case the brake lights will not come on.
4. Does the car have turn signals and a flasher? Check for 6V power ---the main wire is typically fused. Check the fuse.
5. Concerning the circuit breakers. I know there is one behind the dash cluster and it's the main CB for the entire harness (maybe 30 amps?). If this main circuit breaker fails nothing will work (except possibly the horns). I believe there's also a second CB on, or very close to, the main light switch. Do the front lights turn on OK ---if so, this circuit breaker is OK and probably not the reason why the tail lights won't work.

Hope this helps a bit...

I assume that when you turn on (let's say) the parking lights, you DO have parking lights, but you don't have taillights. Right? (Because if you don't have parking lights OR taillights, the problem may be somewhere besides the taillights.)

How are your taillight grounds? You could take a test wire with alligator clamps at each end, clamp to some known ground on the car, and touch the other end to the taillight socket (not the contact). If this lights the taillight, your problem is a bad ground of the socket.

I have tail lights now and one parking light, but still no turn signals. Headlights work as they should. Turns out it was a contact issue inside the switch itself. Also, when the tail lights are turned on, the right turn signal illuminates. I'm assuming that there are some bare/crossed wires (have found some bare already) so I'm proceeding with rewiring and replacing all the bulbs, just waiting for a boatload of primary wire and terminals to show up. Will also do a continuity test on the brake switch. Just need a few rainy days!

If the turn signal lights with the parking/tail lights then you probably have a ground issue in that light.

Tom is right. The majority of lighting issues are to with poor ground. Run a separate wire from the bulb fitting to the chassis.

Well, the more things I've fixed, the more problems I find! I've just decided I'll be ahead doing a complete re-wire on it. I'm finished with the front lights and behind the grille, new wires back to the dimmer. Looks like it's going to be a cramped job under dash. Any hints or tricks to gain better access? Looks like it'll be a bear to pull the inst. cluster. This isn't going to be easy for me at all, messed up my lower back this winter, don't contort so good, lol..

You mentioned turn signal and taillights doing weird stuff ,look close at the filaments in the lamps. I had one short internally when one element broke and touched the other. Was making all sorts of weird stuff happen .

Make sure the bulb is installed correctly. If one side is pushed in wrong- long slot in the short slot and Vise-versa, can cause this same issue. It is commonly described as feedback. As you also mentioned, one bare wire laying on another!!