Our truck has similar specs to this. I believe our wheelbase is 114" and the box is 12'. If I had it to do over again I would try to reduce the rear overhang as much as possible as the rear cantilevered weight is wreaking havoc with the already questionable ride quality of the front suspension. Keep in mind that you will most likely want to mount two spares onto the back of the truck adding an extra 18" of length and significant weight. We are currently working on shifting weight forward as much as possible by installing a big winch and a front bumper with storage built in for heavy stuff like tire chains and jacks.
On a side note, I love the Bliss Mobil 11' pop top. If our habitat ever falls apart I will be going with one of these.