You don't have to eliminate the key. If you don't want to mess with the wiring or if it's some fancy factory anti-theft device: you just need to disable the steering lock. Follow the factory/haynes/internets instructions for removing the ignition key cylinder on your car, complete with that little bolt that goes through the steering column and locks it up. Remove the bolt from the mechanism and put the ignition cylinder back on, or skip removing the bolt and just attach the ignition cylinder to something solid where you can reach it and turn the ignition key. Done!
Of course, you can just wire all wires except "start" to "hot at all times", and then wire the "start" wire to a nice 10-20 amp starter button/household switch/whatever. But just removing the steering lock is easier if you don't want to mess with the wiring.
K Car Stalker