Looking for a manual for a 1940's vintage Allis Chalmers ( R 250 ) direct acting rocker contact DC voltage regulator, 125 volts, 0.75 amps.,60.0 ohms, 1.2/10.0 amps. This for a 12V278A Cleveland diesel electric tug. Any recommendation on a refit to AVR. This unit excites the prime mover DC generator. I can't post a picture as the limit has been reached. First hand info welcome.