I want to do this cheap but effective starter kill. http://www.bfranker.badz28.com/fbody/starterkill.htm
Does anyone know the part number of the relay used? I don't want to look like an idiot going into autozone without a part number.

 

Just use ANY 5-pin relay. Automotive...marine...they'll all work.

 

Are there any kind of power ratings that I need to look for? I don't want to fry it by sending too much current/voltage through it and not be able to start my car.

 

Your interrupting an existing circuit, the killer won't pull any more current than the circuit it's intterupting, as for the relay just ask for a fan, or fuel pump control relay, most relays will have the pin-out printed somewhere on the body.

This is the same as a PCs Ctrl-Alt Del reboot sequence. This method is used in stock, and aftermarket alarms, thieves have only to take the time to try any switches within arm's reach (headlights, running lights..etc,) and that's the point thieves don't like to invest too much time in stealing a car.