91 olds 98 regency ignition wiring

Ok I want to put in a toggle switch to turn the car on and off. I looked at the wiring chart which gives 4 wires off of the Ignition switch harness. First question, are these heavier gauge than most of the wires underneath the dash? I have a few that look to be 12 gage possibly and trying to determine if those are the wires i'm trying to locate. Secondly, which wire will kill the car? Logic tells me it's not the accessory, but I still have starter, ignition and constant power wires. I would assume the 12v constant but I don't want to start cutting wires and be wrong.    Any help would be greatly appreciated! Thanks! robert

https://www.the12volt.com/info/diagrams.asp#si Very top, Start Interrupts. Welcome to the12volt.com/forums. Be sure to use the search feature before you post. If you need more help, we're here to help you out. Cheersrtfm