A few more suggestions:
- Before starting to build think about how the drawer will be held down in your Jeep. If you have strong cargo loops on the floor you can potentially use turnbuckles.
- Make the system easy to remove in case you need to carry large items. Mine comes out in just a few minutes.
- If you go with drawer slides get ones that lock in both the closed and open positions. It's a real pain if your drawer tries to slide shut when parked on an incline.
- Use threadlock on any screws that go into metal, they can vibrate loose over time.
- +1 to Boort's suggestion of using light weight materials. I've used 1/2" plywood on a couple drawers and it worked well. Check with your local lumber yard for lightweight plywood options.
- +1 also to Boort's suggestion about thinking about what you plan to put in the drawers. Mine is sized so that I can fit (barely) my tool bag but still have the box be the height of the wheel wells to keep my sleeping platform low.
Drawer for a 3rd gen 4Runner
Drawers for a 4th gen 4Runner, which might look suspiciously like TheAdventureIndex ones that Boort linked to.