EDIT: Thanks to input from KamperBob, I did another plan view overlay for the truck, which can be found a few posts down, post #71
If you do have an aerocap in mind, this might be useful as well:
It's tough to see what is the truck, but that gives an idea for plan taper down the sides (if you can stand to lose a couple inches, although it doesn't seem to come in much more than the thickness of the bedsides). This is the newer generation of Ram, but as far as this goes, it will be pretty close to your truck.