interesting hook-up

OK, so maybe i misstated a bit, but anyways, heres the question:

I want to install a tachometer on my 95 corolla (actually a geo prizm...but lets not get technical) so im going to go to a junk yard and grab a whole new guage panel/cluster, spedomemeter, gas, temp etc. and install it.

Before I do this, Im looking for help as to how to know weather or not my car already has the hook-ups. I checked for thr requisite green wire on the ignition coil, and it appears to go to the speedometer cluster. But is there something tell tale i can check for, b/c right now, after I have removed the instrumentation panel, I can't just look and say, 'oh, there's the hook up!'.
Would it normally be the case that if the car DOESN'T come with a tach, that the hook-up to the coil would have to be done?? Or is it possible that the leads already in place on some makes/models??

Help here appreciated. Thanks.

Omar

Im not sure this should be displayed in this thread area , perhaps the electrical thread would help you more unless you get lucky in here.

OK, I actually didn't see that section.

Ill look for it and repost it there. Thanks.