Installing After market Tach

I recently purchased a 1997 S -10 with the 4.3.I do quite a bit of towing ,so a tach helps a lot.I've almost installed my sunpro tach but I can't figure out which wire sends the tach signal off the ignition module. I'm afraid of experimenting and blowing a computer or something.I bought the Haynes Manual,but it is too general and doesn't help.Does anyone have any suggestions?I have gone to the dealer and they don't seem interested in giving advise about aftermarket products.A new dash is way too expensive.

the green wire from the tach goes in the positive side of ur coil....there should be a little box right with ur coil, and it will have 2 plug ins on it, and the wire goes in one of those 4 slots on those 2 plug ins, not for sure off hand witch one it is, but u wont blow ur computer or anything just poke aroudn till it works and dont forget to set the switch on the back of the tack for 6 cyl