[MDPotter]

I don't see why you couldn't add a resistor for the tails, we had to for them to work along with the LED flasher. The reason for the resistor on the 64 is because the PCM couldn't see the voltage because the draw from the LED tails was so low.

We didn't run a separate ground and it works just fine - nice and bright. It grounds through the socket in the taillight housing and then through the screws into the taillight housing in the bedside. So make sure that socket is clean - take a piece of emery cloth or sandpaper so things are making good contact. Without a good ground, lights on these trucks don't work. It's possible that your issue is just a ground issue, we had the same problem.