I am on my 3rd '67 Plymouth. All 3 cars have had dash light issues. As long as you are replacing the bulbs, you might want to lightly sand the copper rings around the bulb sockets to remove 55 years of oxidation. Also, sand the 2 little contacts on each bulb holder. There is a flat metal ground strap that runs along the top of the instrument cluster. That strap grounds the 3 screw locations to the dash. Sand any rust off of that and any oxidation along the dash itself where this ground strap makes contact with the dash. I just ungraded to LED lights; and I highly recommend that upgrade. LEDs are so much brighter than the old tiny little incandescent bulbs. If you do decide to go with LEDs remember, polarity matters with LEDs. If the bulb holders are not orientated correctly to get positive power, they will not work. If that happens, simply rotate the bulb holder 180 degrees and reinstall. Also remember, the dash lights are in series, so each LED will have to have the correct polarity. Once LEDs are installed, bench test the cluster before reinstalling. On the instrument panel, there are 2 locations where the wiring harness plugs in, (one for the left side of the cluster, one for the right). Each location had 5 prongs. The middle prong of each attachment point is where the dash lights get their power from. Run 12 volts to the middle prong on each side of the back of the cluster and run the ground to the aforementioned ground strap. You can also test the turn signal and high beam indicators, but I do not remember which prongs send power to those indicators. If any of the LEDs do not light up, simply remove, rotate 180 degrees and reinstall. Also, light switches are cheap. I replaced my light switch while I had everything apart as well. Have fun.
