Just picked up a set of these Hi-lift mounts from Ellis Precision.

They come with tamperproof torx bits (and matching key) to clamp the mount to the bumper and instead of a stud on top, it's actually a bolt through the centre to attach to the Hi-lift. These are designed to use the ARB M12 light locks on top to secure the Hi-lift to the mount. Therefore the mount is locked to the bumper and locked to the Hi-lift.

This is a well designed and manufactured product, and unless the thieves want to steal your whole bumper, they won't be getting away with your Hi-lift.

Joel @ Ellis Precision can make your mounts with a custom bore to fit any size bumper or roof rack at no extra charge. They can also be anodized in a variety of colors at no extra charge as well.

 

hard to tell from the angle of the picture, but is it a type of keyed nut that locks/holds the jack in place to the mount?

 

Ya, it's the ARB M12 light locks.

Here's a link to a better picture.

http://www.google.ca/imgres?q=ARB+Li...r:8,s:15,i:121