After doing tons and tons of research and also taking apart the tailgate I learned that the tailgate was really not an option for two reasons.
1.) the sheet metal is thin on it. Causing flexing of the back, outside, of the tailgate. This will cause a lot of rattling and poor sound.
2.) running the amp wires will be moderatly difficult in the stock location without ruining the rubber grommets and boots.
So here's what I did. I picked up one of JL audio's Ported power wedge 8w3v3
This box fits PERFECTLY next to the third row seats. Very small but very powerful. I have pics and it's mounted nicely. The carpet matches and it looks like it should be there. I am using a JL audio XD200/1 amp and a line converter. I also installed a subwoofer control knob on the center counsel behind the parking brake lever.
Doing it this way is a great way to add some serious punch. With it wired this way my factory sub still works so when the kiddos are in the car my stereo sounds the same as before. But when I'm by myself or anything I can make it pound. A lot of people have mistaken it for something way larger! I have some pics and I'll post later when I get home and I figure that out but I'll just say when this thing is hitting hard, don't plan on using your rear view mirror! With the knob you can really dial in the bass just right for rock, country, or pop. Hope this helps.