Instrument Cluster Voltage Regulator

There are several of these out there on the various forums. The one below is one example (http://www.chargersourceguide.com/voltreg.jpg) and includes a potentiometer for fine adjustment. That IC can be placed inside or mounted to the outside of an old regulator (IR) with heat sink. The Integrated circuit (IC) is small enough to mount inside the old fuel gauge and be wired soldered to the terminals from inside the gauge for an original look. I decided to go to the outside set-up. May still try to wire one up.

http://www.chargersourceguide.com/voltagelimiter.html