Help needed

If it's an inertia switch - don't know about in Aussieland but Fords here have had them for years in the trunk. You might be able to scavenge one easy enough and it's wired into the fuel pump relay circuit.
if this is for sanctioning body - the Master cutoff is used in the US. Has to be clearly marked and mounted on the rear of the car where it's accessible regardless of vehicle orientation.