Location of 91 Dodge Ram 350 Ram Voltage Regulator?

Depending on what you have, it's either in the PCM, inside the alternator, or on the fender well.

Should be on the back of or within the alternator housing.

For a 1991 Dodge Truck W350 1 ton P/U 4WD 5.9L FI 8cyl, the regulator is in the engine computer.