Just bought an 1987 GT with t-tops for a daily driver. Cant get the front parking lights ar ANY of the rear lights to work. The head lights and fog lights do work how ever. I replaced all the fuses that were bad, installed a new head light switch and a new brake light switch. Out of ideas....
sounds like it might be a grounding issue. i'd check the 2 grounds that are bolted to the upper part of the radiator supports. they are near the bumbstops for your hood. there should be a small black wire with a ring terminal that has a 7mm green bolt attached to it. i'd check those out and see if they werent ripped off or someone unbolted them as they are the grounds for your light harness.
After ensuring that all bulbs are okay, as well as grounds for the lighting..........
Time to pull out the meter and start testing. Test for power into and out of the BOO (the latter of course needs to be tested with the BOO closed).
For the parking lights, check the parking light terminal on the headlight switch. The wire is brown under the dash but I can't remember if it's also brown egressing the switch. If the parking light terminal is ok, it will be time to start chasing the rest of the circuit.