Unless you are a stickler for all stock and you don't care about fires, use a voltmeter instead. Many people knowledgeable about electrics do not recommend using an ammeter. It requires ALL the power/current from the generator/reg to go inside the car and back out to the battery so it can read charge and discharge, which will require larger wire because of the longer length. In the 60's they used a shunt in the engine compartment, so the meter only sees a small amount of the total power. Voltmeter only needs a 12V source and measures the voltage storage level of the battery. 14.5V= everythings OK, dropping below that= something's wrong, rising above that= something's wrong. Fires and burnt wires have been experienced by many who have used ammeters on old cars/trucks.
