Tach signal?
 

1.) Where does the tach get it's signal from? Alternator? Or is it triggered like the 2nd gens?

2.) The factory tach (on top of the dash), has about a 2 foot lead with four wires that go into a rectangular plug, Where does this plug into?

3.) Is there a way to test this tach before installing?

Thanks Rick

Theres a plug under the dash by steering colum on left side.

My understanding is that the '92 and '93 trucks have factory tach wiring, as stated by loch. These trucks get the signal from a sensor at the crank pulley.