Thanks to everyone for the guidance, but didn't have any luck getting my right rear brake light to work or the right rear turn signal.

Using your suggestions, I checked the following items:

1) I verified that I have 1156 bulbs in the backup sockets and the others have 1157's in the others. Everything is solid.

2) Checked the single black ground wire on the rear harness (the one located on the truck latch support). Again, it a new harness from Ames and it's attached to the same place that the factory harness was attached. I even used a Dremel tool to clean any paint, rust or debris off the surface before attaching the ground. I can't find any other grounds to the rear harness anywhere. If there's something else I'm missing, please help me out.

3) I ran a wire from the negative battery terminal to the single ground wire on the truck latch - no luck. Then also tried to make contact against the taillight housing, in case it was the actual ground to the car body..no luck either.

4) Lastly, after all else failed, I unscrewed the black ground wire on the rear wiring harness to see if that would effect the light situation, but it didn't. The light still worked the same even though it was disconnected.

I guess I'm going to need to get another volt meter so I can start checking things out further.