1988 Ford F-150 gauges not reading properly

If you are making the reference that I believe you are, what you are refering to is called "VREF" (Voltage REFerence). It is a signal sent out to a majority of the sensors at 5 volts. It is regulated by the PCM (Powertrain Control Module) and is used to nullify voltage fluctuations from the alternator in a 12 volt system. It is intigrated into the computer and cannot be replaced without replacing the computer. However, I do not believe that you have all the information needed to warrant replacing the PCM. You need to take the vehicle someplace that can read the data that the computer is seeing. Your problem (in my opinion based on the current info) is in the instrument cluster.