The all weather package would probably be the best option for you. You can get it with the FDI manual, gives you tow hooks, engine block heater, and other options. I believe it also includes the oil cooler (which gives you the 2000lb tow rating).
I have a FDII, and LOVE it, (check my links in my sig) but would not recommend it, unless you plan on actually going off road often. The FDI is plenty capable enough, especially if you don't plan on actually rock crawling.