Only some of the dash lights work

The common reason is that the bulbs themselves fail. They are replaceable but you need to remove the gauge cluster from the dash to get to the back side to change the bulbs. While it is out I would change all of them, the rest are the same age and could fail at any time.

Step 1 - Disconnect the battery ground.

2. Remove accessory trim plate as follows:
a. Pry steering column collar rearward, using a suitable tool, and remove.
B. Remove outer air deflectors, then the two screws behind the deflector openings.
C. Remove screw from behind steering column collar.
D. On models less console, open ashtray and remove trim plate attaching screws.
E. On models with console, remove four screws from ashtray trim cover, then ashtray trim cover. Remove trim plate attaching screws.
F. On all models, pull trim plate rearward to release clips, then remove accessory trim plate, Fig. 9.
3. Remove screws attaching cluster trim plate, then trim plate, Fig. 10.
4. Remove steering column trim collar and trim plate.
5. Disconnect shift indicator clip from steering column shift bowl. This clip has a short cable that pulls the shift indicator to the correct position.
6. Remove cluster assembly attaching bolts, Fig. 11, then pull cluster rearward.
7. Disconnect speedometer cable from cluster. You will find a spring retainer, push it in toward the cluster and pull the cable back to disengage.
8. Remove cluster assembly. Replace the bulbs as listed in the first image.
9. Reverse procedure to install.

There are different bulbs in different locations, the bulbs for the gauges should be number 168 bulbs. There are also 194 bulbs in the indicators and places like the oil charge and other warning lights.