IN that case you don't want a fuel pump shutoff switch, you want a kill starter switch.
Look for the wiring diagram in the Haynes manual or take it to any local competent mechanic, he or she should be able to wire up a kill switch to your starter. A car can't go anywherw without a s atrter and your alot safer than cutting off fuel since you can't crank the car over AT ALL>
I had a starter kill switch (of course the LS already comes stock with a starter kill alarm system) hooked hard lined to my starter that was in my glovebox compartment, which i rarely ever use only when I am leaving it in areally bad place. My second system was having an ignition button installed in the stock lighter area. It was hard wired so that cranking the key would do nothing, rather you would have to turn the key on, know where the starter button is and press that instead.
So a strt up sequence in my old car was like this:
1) Get in car, unlock glove compartment.
2) Turn on starter switch
3) Put key in and turn to ON position
4) FLip open the cigarette lighter ash tray front plate
5) Depress the said starter button to start the car.
It amazed alot of my friends and provided alot of extra security. You wouldn't believe how hard it would be to start my car without knowing how to. Not to mention since everything is hard wired directly to the starter you can't jump start the car in the normal fashion. HOpe that helps, I don't think it's covered in any sort of how to guide since you will need a competent mechanic who knows what their doing as it involves quite some serious soldering and rewiring.