Dash lights

I think OEM is/was #158. #194 is close enough. Typically only 4 of the bulbs are illumination. When one goes out a portion of the display will be dark, one half/side of the speedometer for example. Other faults cause consistent dim ( they never were very bright to begin with ). Dimmer rheostat in the headlight switch is the positive source. It can be the fault. You may notice that the round terminals on board pins are oval shaped. They may not contact the pin very well. Some are mated so well that they pull the male pin out of the board while the next contacts at 2 small lines.
The screws that attach the circuit board to the housing are part of the chassis ground path. Cleaning circuit board connections should include all those spots. The screws that attach the assembly to the dash are also part of the ground path. Adding a actual ground wire somewhere may not help but couldn't hurt. For my 67 b'cuda panel I added a ground wire with ring terminal and toothed washer at the lower screw of center pod where my performance indicator/vacuum gauge is. About 4 inches away is male female spade terminals so the added wire will unplug like most other wires. My ground wire ends at a screw with toothed washer added behind the left kick panel.
If you decide you will install LEDs, you will need this ground wire connected so you can power up the panel while it hangs out of the dash and rotate those bulbs 180 degrees as needed to get their polarity correct.