I have a comment on the positive battery cable switch shown in a post above. A few years ago my friend purchased one for his 428 Cobra powered Shelby GT500. The engine would not turn over after the switch was installed. There isn't enough contact area for a car with a high current draw. I have seen these switches work on small block Mustangs but my friend could never get it to work on his GT500. It may work on the Crossfire.