I'm trying to install a little 3" tachometer but I can't seem find the correct wire coming from the coil or distributor. I know my green wire off the tach is the "signal wire" but when I go searching for a green or brown wire under the hood I'm not finding it. 1990 GMC C1500 \ 5.7L 350 Here's a shot of the distr. and I'll get one of the coil tomorrow when the sun is out. Any help greatly appreciated. The distributor has a connector labeled ABCD on top, just FYI. Thank you.