Shut off switches.

I've seen 'em inside the trunk, under the trunk, thru the bumper, thru the tail lights, and a friend even has one in the dash of his Dart. My favorite is to put the switch on a tab, welded to the rollcage, with a rod thru the tail light panel, to make it work. With a close second, of putting it all below the bumper, on a bracket, so that no paint has to be disturbed.