[skyking]

I think you will get the 20 in average driving in Montana, so long as you keep it under 65 on the highway. Not too much stop and go in that state
The autos have a higher OD at 0.69, so the RPM is down in the favorable range.
Free spin kit is 1500, now all that separates it from a 2wd is lack of independent front axle, a little bit of weight and about 4" of height/frontal area.
With a free spin and everything else equal, I think a 2wd will have a 2 MPG advantage in the long haul.
Way cheaper and handier than a side by side for basic exploring, and the ability to take your trailer into different spots. My 2wd would get stuck on wet grass in the wrong conditions, and it was limited slip.