All the dash gauges are susceptible to problems, but many times they can be repaired.
Generally the speedo just works. When it stops, it's usually a problem with the VSS on the transmission. They don't often break (which is good, because they're pretty much unavailable OEM or aftermarket now)- it's often a wiring issue.
Trip meter and odometer problems are usually caused by deterioration of a small gear in the mechanism. They are available in the aftermarket. See all the repair options on the odometer page.
Fuel and Temp Gauges______________________
These gauges become erratic or stop working because the slosh board goes bad. Removing it will often revive the gauges, as will replacing the capacitors on the board. This one has new caps (blue and black, next to each other).
No, low, or half-speed tach reading can hard to diagnose. People have reported cold solder joints as a problem. Sometimes just pulling the cluster and removing the tach will revive it. But not often.
Dimitri pointed out there's a filter in the circuit that could contribute. It's located on the frame rail, driver's side, just below the air filter, thusly:
It looks to have a Bosch number on it: 0 119 910 002. The Ford number on it is: 86GB17K499AA.
Lazy Tach: something that might help variances in accuracy is a potentiometer inside the tach. Lee Shepherd points out the contacts might be dirty; mark its original setting and turn several times to clean. Contact cleaner will help, too.