I got your message. Here is the rebuilt Tach:

http://rides.webshots.com/photo/2896660240080243953BkudSM

Here is the wiring diagram:
http://rides.webshots.com/photo/2753742480080243953xyrPLo

I had it rebuilt here: http://www.bobsspeedometer.com/bobs/

It was added by the firetruck builder(Oren) in 1952. When I went to rebuild it, I discovered they no longer make the battery that went into the firewall mounted part. I had to have the guts removed and electronic modual installed. From the outside view, you'll never know the difference.