Installing a kill switch of fuel pump

If you put the switch in the engine bay you would have to open the hood every single time to start vehicle, what a PITA that would be. I'd run it to the cab. I also believe they make remote starter/anti theft kits that include such a kill switch that requires a specific function before allowing vehicle to start.

Hide the switch in an easy place to access, perhaps in the console. You can get key switches or you can disguise it as something else.

All great suggestions. Thanks. Do you guys have any idea what color wire it is? Maybe what part of the harness it runs in? Was looking for it tonight. Not any luck yet.

Try www.f150forum.com, I saw several topics on kill switches there, the most commonsense place to run it is to the fuel pump relay as you mentioned doing. I would look for a year specific wire diagram for your truck for that particular circuit, on the chance the colors for woring changed between other years.