A sheriff deputy told me you can spray the bottom of the catalytic converter with high temp white paint and then etch your driver's license number on the converter. The thief will see the white paint in the dark and maybe even the etching and will realize precautions have been taken. This is just a deterrent, but since a thief will have to sand the etching off and a buyer will notice this, the thief will move on to another vehicle.
595 Round Rock West Drive, Ste. 503Round Rock, TX email@example.com