Hey y'all, I found this ol' tach in my parts arsenal, but I have no idea how to hook it up. I cannot find it in any of my books, or online either; with no part number it's quite hard. None of my other tachs have the same color coding, either.

Anyway, I'm installing it in a 1975 Dodge W300 dually with a 360. Looking at my service manual, the optional tach has 4 wires, like this aftermarket tach, but the colors are different. I have no idea how to disassemble this tach to trace the wires, and I don't want to risk hooking it up to the wrong leads.

According to my service manual, black (BK) attaches to the coil, white (WH) is ground, green (GR) goes to ignition accessories in the fuse box, and orange (OR) goes to the instrument panel for lighting.

The wires on my tach, (link to photo below), are white, blue, red, and black. All my internet research pulls up either two red and two black, or red, black, white and green on tachs.

http://viewmorepics.myspace.com/inde...ageID=22701997

Thanks for the help!