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I just tied a switch into my distributor hot wire. I've heard of using a switch to send ignition power to horns when trying to start.
If you are looking to break the crank signal to the S terminal on the starter solenoid, go to the NSS instead of cutting wires. This is still easily overcome with a screwdriver so you'd be better off disabling the ignition system. Crank, no start makes noise, floods engine scares away would be thief.