OK so how does one go about changing the dash/instrument lights, speedo, tach, gauges.. ouch

 

Well I can tell you what I did on my 91 FB. I believe the early thirdgens are not much different though. Major difference is the orange plastic back which needs to be painted, otherwise everything will still have an orange hue to it. On the later ones the bulbs had orange plastic caps.

First you'll need to remove the dash, there are 4 screws in the vent:


and from underneath:


Dash off:


and some more plastic trims removed, actually there are quite a lot of parts to remove to get to the instrument cluster

 

Then there is the cluster, the bulbs are located in those sockets that can be unscrewed easily. I actually replaced only the ones that light up permanently. I left the original bulbs for the turn signals, headlights and idiot lights as when replaced by led's they made some strange blinking and that awful beep came on too. I think you'd have to replace a relay to get it to work properly, maybe someone can chime in on this.

I believe I replaced the bulbs in the grey sockets only


These are the original wedge base bulbs with the orange caps on the 91 bird:

 

Then there is that weird light that illuminates the switches to the left:


I carefully pried it open


I soldered in a neutral white LED and a resistor


and I replaced the orange film with a clear one


I don't remember the resistor I used, anyway you'd have to try out. Mine is actually a little bright.

 

As for the HVAC and radio I didn't change anything yet. So I don't know exactly what you'd have to use.

I used these LEDs from superbrightleds for the instrument cluster (natural white)

https://www.superbrightleds.com/more...edge-base/199/

Those did the trick for me and they are dimmable, too. Brightness pretty perfect, not too bright at night and not too dim in the day

On the HVAC and shifter plate you'll need the mini wedge base LEDs though

https://www.superbrightleds.com/more...edge-base/226/

Actually I'm not sure how many of them are needed. Search the forum for more information

For the map lights I got two of those, because the other ones mentioned were not bright enough and they are a little too wide. Got them on ebay

 

Oh yes and for the dome light I first ordered a festoon led from superbright, but that one was WAY too dim. So I ordered a panel like this, now the interior lights up like on a sunny day in the mountains!

 

Hope that helps. Don't know much about changing the gauges themselves. Maybe this is of some use
http://www.whitegauges.net/categories/Pontiac/Firebird/