Installing an Aftermarket Tach

[norge187]

I just bought a aftermarket tach and I can wire it up completely except for the most important detail. I can't find for the life of me the tach lead. Does anyone know of a way to maybe piggy back it off the main lead coming off the tach behind the dash. I'm realy not sure where to hook it up. I don't think you can even hook it up through the negative wire off the coil pack. Any hints would be greatly appreciated. I just need need to figure out where to go realy to make the actual aftermarket tach work. Lemme know i would greatly appreciate it.