[Aussie Mike]

There's some nice big red buttons available for industrial switch gear. I adapted one for my start button.

Mine's not a superformance but the theory is the same. I've set mine up so you can use either the key or the start button to crank the engine. The Start button trips a seperate relay to switch the start relay. The power for the start button relay comes from the ignition switch circuit so if the ignition is in the off position or accessory position the start button wont work. It only goes live when the key is in the ignition on position. No need for kill switches etc.

I am running a seperate electronic imobiliser to kill the fuel pumps and ECU etc but this is an engineering requrement for registration down here.

It sounds a bit complicated but it's actually very simple. I'll try and draw a picture of the circuit and post it up here.

Cheers