Just got done fixing all of my lighting issues in the 73 Firebird. My rear driver side light was out. The driver side brake light was out, the passenger side backup light was out. The left side of the dash wasn't lighting up either.
There are 2 brake-lights each side, and 1 backup light. They each use a double pole bulb, but the backup lights don't use one side of the pole. (You can't use a single pole bulb because the pole would be aligned in the center which won't work for the stock receptacles )
The lights at the rear were the easiest to repair, you can reach them via the trunk, just twist the receptacle and it pops out. My favorite local parts store had the replacement bulbs. A couple of the receptacles were pretty corroded and rusted. I was able to revive all but one using a battery cleaning brush. Went back to the parts store to get a replacement receptacle, we found only one that matched, and they only had the ONE. Bought a crimp wiring kit as well. Clipped the original receptacle, off, stripped both sets of wires, connected them with the crimp fitting, and reinstalled. I think a couple of the other receptacles are pretty iffy, if I have any further problems with them I'll just replace the receptacle like I did with the backup light.
The lions share of the time this weekend was spent figuring out how to get into the instrument panel to replace the dead lamps. After probing the dash and figuring out that it wasn't a press fit, I did some research on how to take it out.
Found a great video of a guy installing a dash cap () that showed how I had to remove the panel underneath the steering wheel by removing two screw like retainers. With that removed there are two 5/16 Hex #10 2" machine screws that go into the bottom of the instrument panel. I was able to able to remove one of them without a problem, the other one's head was hopelessly rounded over. Off to the parts store again. I found a set of Irwin Bolt extractors that included a 5/16 remover. http://www.irwin.com/irwin/consumer/jhtml/detail.jhtml?prodId=IrwinProd100518. Finding replacement 5/16 Hex #10 2"'s long turned out to be more difficult. Checked two auto parts stores, home depot, and then finally Lowes. At Lowes I found a match, except that it's zinc not black oxide coated like the original, and is slotted as well as hex. But that would work for my purposes, I certainly wasn't going to put the rounded one back in.
Next step is there are three Phillips head screws that need to be removed to get the face off of the instrument panel, they are hidden at the underside of the top of the dash. Those were simple to remove with my flex screwdriver and a magnetic bit. This is as far as my you-tube video would take me. I next had to figure out where the lamps were. I ended up taking off more bolts than I needed to, and breaking a little plastic lens thats used to shuttle light from the left instrument bay to the backside of the "washer" label. There's a number of screws that hold the plastic face on the instruments, and there's a similar number of screws that hold on the black plastic fascia that sits in front of the gauges, and allow the instrument panel to be loose inside the cavity. I could see some of the lamps but the ones I needed to replace couldn't be gotten to from the front. I finally figured out I had to get to the BACK of the instrument cluster, they were miniature versions of the trunk lights, I unscrewed the receptacle then I could replace the lamp. I couldn't get the instrument panel out at all. Back to the internet, come to find out the speedo cable needs to be removed to allow you to get enough room to maneuver and expose the rear of the instrument panel. There is a release right next to the speedo cable, reaching in through the underside of the dash I could push the speedo cable and the release and it came off. I was then able to maneuver the instrument panel so that I could at least feel the rear. It looks like to totally free the instrument panel, I would have to take the steering wheel assembly out, and theres a wiring harness that would need to be removed. Luckily what I couldn't see I could do by feel. All told theres about 8 lamps in the instrument panel, only about 4 that actually light the compartment, the rest are for things like trouble lamps, turn signals etc. With the bulbs that were out replaced and tested, I began reassembly. I started with super-gluing the lens that I broke back together, it had a nice clean break, super-gluing seemed to do the trick. Put the speedo cable back on, it just snapped back in place. Put the black plastic mask back on, then the clear plastic face. Putting the dash face back on was a lot harder than taking it off, I can't explain why. Perhaps the contortions I was having to do with my body to put all those screws back in.
Tested all the lights again, and then went on a test-drive. It was the first time I've been able to see the fuel gauge at night, fantastic.