Interesting. I added a soft toneau cover this summer to my Ford and the store had a swing out locking storage unit that could hold handguns and other things. I had one installed. It has spot on the hinge set up to add a lock so it can't be pulled off hinge pin.
I posted somewhere that there is a padded aluminum rack that bolts onto your sunvisor mounts(put them back onto the rack). That gives you instant access to your firearm. There are also several types of pouches/racks that mount them onto your seats. I like having them where you can get to them quickly without having to stop, unlock and outside cabinet and get back into your vehicle.
I like it....but....I certainly wouldn't leave my rifles unattended, even while locked in that compartment. Savvy thieves, will target these trucks and I'm sure those boxes are not that difficult to pry open.