Buy a Haynes Repair manual, they have wiring diagrams for basically everything you could think of. Thats the only way I could figure out my speaker system when I chopped them all putting in my Pioneer deck.
Well if it helps at all, when I was installing my gauges and msd box I found there was a big blue wire coming from the actually key part of the ignition. This was the power wire that only went to 12v when the key was turned on.
If you can´t find a diagram, pull apart the column and use a multimeter and simulate what you need with the ignition, find the wire that´s reading like 12.43v or whatever it was for me.
Yeah. Haynes manual oughta be a safe bet for a wiring diagram. Speaking of ignition switches, I know that was replaced like 3 of 4 times in my 91 before I bought it. I think it wasn´t fully shutting everything off, so the battery kept getting drained. Repair shop musta been kinda clueless "fixing" it 2 or 3 times. Finally it went to the Ford dealer and they got it right.
No problems since she´s been mine!!!