The back lighting on my 83 T/A dash guages is terrible at best, dim and wierd shade of yellow. Anyway to get a better and brighter backlight system

 

There are likely a number of bulbs burnt out. Best bet is to take out the cluster and replace all the bulbs with some new bulbs, preferably super-whites if you can find them. If you're feeling creative, take apart the cluster from the front, gauges and all, and put a fresh coat of semi-gloss or glossy white paint inside the housing for better reflection of the bulbs.

 

Bulbs get old and they turn dark, even if they are working they will be dim. Note usually there are two different bulbs in the cluster. 194s are for the constant back lights, and 168s for the signal and warning lights. For brighter lighting you can use the 168s in all sockets - but they do burn out quicker. Tips on taking out the cluster, note two small nuts in bottom inside of cluster, hard to see. And the speedo cable is sometimes a two piece deal, unhook out under the hood and push it through the firewall to allow the cluster to come out far enough to disconnect the inner cable at the speedometer. When you get the cluster out you can easily take it apart and polish the lens, really makes it look nice.