Some options (I can't recommend any but I'm posting what I've found):



A simple way to stop thieves from stealing tailgates - ABC15 Arizona

Other options:

Park with the rear of your vehicle backed up close to a building or residence to prevent the tailgate from being able to be let down.

Engrave your VIN into your tailgate. It should be visible but not to the point that it becomes an eye sore or is aesthetically unpleasing.

 

I'd worry more about that Cobra jet than the tail gate!