Interesting you mention the far right light in the cluster. The ground gets to the cluster from pin 7 of the connector, and then it goes to the far right bulb and to the metal of the cluster through a screw, and then the rest of the printed circuit ground trace gets ground from the screw on the other side of the cluster. So if those 2 screws are not clean and are not making good contact with the metal trace in your new printed circuit, you could have a lack of proper ground to the cluster lights other than the far right one. Don't know if that is the whole problem, though. Here is a diagram of the cluster printed circuit.
http://67-72chevytrucks.com/vboard/s...d.php?t=709847