I'll see if I can describe how my mounts work (and how I will do them in my new truck as well).
For the bottom of the net I have a length of 3/8" solid bar stock. One end has a washer welded on it about 1" from the end, and a hole drilled through it about 1/4" from the end. That end slides into a tab welded to the cage, then a washer goes on and a hairpin clip through the hole. The other end of that bar has the end of a seatbelt metal buckle welded to it, with the seatbelt still attached. I welded a tab to the cage below that point, with a slot through it that the seatbelt can be passed through, then looped back on itself the way a harness or a kid's car seat would secure. This allows me to adjust the tension in the net. The top of the net is a similar 3/8" bar with a washer welded to it about 2" from the end, and the end has been machined to a dull point to make insertion into a hole easier. On the cage there is a tab with a hole that I poke that end into. The front end of the top bar has a seat belt latch welded to it, with the mating part of the latch welded to the cage. The net normally drops down out of the way, and to raise it I poke the top bar's end into the top rear tab, and snap the seat belt buckle into place. LOL, a picture could have saved a lot of typing!