IIRC, an easier option has been to kill power to the injectors, since the ignition system has a much higher amperage to deal with. That way, you wont have to hack the steering column or find a super-duty relay.
The downside is a Check Engine Light for cylinder #x misfire or similar.
If you want the full package, get a push-button start
Here's an
Instructable to do both.
RH77