I searched SO MANY different forums on how to install anaftermarket tach on a KA. Well, having found nothing I startedto test the wires on the coil and I have successfully installed atach/shift-light.
No one wanted my 5" monster tach that I had lying in mycloset for a year since selling my Mustang, so I put the tach tosome good use.
Here are the pics (and the last pic tells you which wires to tap into):
http://240sx.cubicdesign.com/picpage10.php