'01 R/T here (5.9, 46RE, 3.92 gears). It's not a DD, but I do like driving it. Around town, I can get 14mpg if I am somewhat careful. 16 is fairly easy on the highway, though I do have headers, full 3" system from aftermarket Y-pipe back, Fastman TB, and K&N FIPK. Mine just turned 100K with the only problems being a rear door lock actuator switch failure (causing automatic locking and relocking doors during driving) and driver's side glass regulator failure (bottom cable guide broken). Both easy fixes.

The '01 is AWD all the time, electronically selectable to 4WD high and 4WD low. Also has
rack and pinion steering - someone should correct me, but I thought earlier models had a box. If memory serves, the '00 and back are 2WD all the time, selectable manually with a cabin lever to 4WD, so those years might get slightly better fuel economy. (I did get 19.1 mpg on a Seattle round trip once doing 55mph the whole way - just to prove to my wife it could be done. She averages 20.5mpg in her Toyota Venza.)

Good luck in your quest.

FWIW, the Grand Cherokee is not a bad vehicle. My sister has one - '04 Laredo with the inline 6 4.0 liter. 42RE. 2WD selectable with a cabin lever to 4WD high or lo. She gets around 18mpg or so with a lead foot. Front axle is of course the solid type, so perhaps a little more durable than the IFS on the Durango. Front diff on the D is "Corporate 205mm". On the WJ is a Dana, IIRC.
Not trying to dissuade you from the D, but it's an idea.