I've had the headliner out of the quad cab Dodge's a couple of times (I have an '07). Honestly, there isn't a simple solution for installing hooks the way you are suggesting. You would almost have to cut holes into the headliner itself so that you can access the body under it. There is a 2" or so cavity between the headliner and the cab in that area, so simply putting a screw through will only catch on the thin fiberglass of the headliner.
With that said, I hope someone has a solution to this. This could solve some stuff for me as well and like a dope, I never even considered using the back seat for a closet.
