ive been working on this for the last week. I used an old tail lamp housing for mock up and when everyting fits ill move it over to a usable housing. Yes the switch needs to kill the motor and all power wired to the positive side. You do not need a steel firewall if you use a sealed and externally vented battery box. Jegs and Moroso sells the vented plastic box that will pass tech. There are several different methods to wiring your switch. you will need to study them and pick the one that suits your build. I use an alternator cut off solenoid mounted next to the alternator and wired back to my four pole switch.