Gauge issues - 66 Valiant

We've got a 66 ragtop that has had this issue for some time now and I just can't seem to track down the problem.

First, a little history, the car definitely had a melt down at some point as the fuseable link had been replaced and the wiring harness was a mess. I replaced the entire dash wiring harness.

What was happening is the gas gauge would do little to nothing. It would occasionally move up and then eventually go back to empty. The temp gauge looked like it worked fine until you put the headlights on at which point it would peg and stay there.

Others advised me that they thought it was a grounding issue so yesterday, I ran a ground wire from one of the ground points on the PCB.

Now, I get nothing out of either the gas or temp. They will not move. I did test both sending units by grounding them and they both did peg so I don't believe it to be an issue with the sending units.

I have already replaced the voltage regulator and I had another voltage limiter (back of the cluster) and swapped that in there as well with no change. That was all done prior to the ground wire yesterday.

I'm getting frustrated aty this point.

Ideas?