Iinstalling a kill switch?

HI,I would like to install a Kill Switch in my 95 Ford F-150. Should I add the kill switch to the fuel pump or the ignition switch? Why do people choose one over the other? What is the minimal wire size I can use and add the switch to the positive side only? What type switch is recommended?Tom

I would kill the fuel. If you kill the spark, the fuel could still be pumping for a little and may cause problems. A spark in an empty cylinder will cause no harm. I would use the same size wire as is going to the pump.

I would kill the fuel. If you kill the spark, the fuel could still be pumping for a little and may cause problems. A spark in an empty cylinder will cause no harm. I would use the same size wire as is going to the pump.

Any ideas on how to wire in a fake kill switch to siren that can't be turned off for a set amount of time?