I am experiencing problems with my brake and turn signal on the right rear side on my 69' Firebird.

Here's the exact problem:
- All of my lights seem to work great, EXCEPT for the right rear taillight and right rear turn signal. Now, if I turn the headlights, the right rear taillight will light up, but even though it lights up, the right rear taillight still does tight-up when the brake is applied and the turn signal also doesn't work on the right rear taillight.

I have ordered a rear wiring harness from Ames Performance, replaced it and no luck.
I then replaced both turn signal flashers (Part# 552) and that didn't fix the problem.
I also swapped out the light bulbs from right to left and that didn't work.
Checked my fuses, but they are not blown.

At this point I am not sure what to check or replace next.

Any help or advice you can provide would be great.

Craig