Ford ignition switches often use a white/pink wire - to go from
Either - ignition switch to the transmission on an auto,
or the ignition switch to the clutch pedal on standard trans.
This can be confirmed with a test light or volt meter.
Automatic goes from ignition switch to neutral safety switch on transmission (to only allow the engine to be started in neutral or park)
Standard transmission goes from ignition switch to a switch on the clutch pedal (only allows the engine to start with the clutch pedal pushed all the way in).
If you interrupt that white/pink wire (please confirm first with a test light or volt meter) with a toggle switch, it will prevent the vehicle from being started no matter what gear it is in. Auto or stick.
Inertia switch shuts off power to fuel pump in an accident.
I would not mess with the inertia switch at all, and leave that system intact for safety. Way safer to kill the ignition.