[fortyfords]

A 64 ford mustang instrument voltage regulator is small and uses the flag type terminals and is available at the auto parts store, very easy to install and mount. But the batt gauge is a volt meter so you must put a variable resistor in series with the gauge, adjust the resistor till the gauge needle reads at the top of the first red bar. Take the variable resistor out and read the resistance and then install a fixed resistor of that value and install in series with the voltmeter. I did this on my forty and it worked for me for many years. The gauge needle will be in the green when going down the road and in the yellow band with the lights on and in the red band when the alt. isn't working. The top red band is when the alt. is overcharging. Good luck