From my experience I would stay far away from an Exploder or Durango.
Grand Cherokee would have the same drivetrain as a 1/2 ton Dodge and will get about the same mileage from what I've seen.
I'd look for something like this.
About the same as an F150, but with a nicer inside and more room.
The 5.4L did have a habit of popping the plugs out if the coil pack or plug is bad, but it's not that hard of a fix.
I had a couple company trucks (F250) with that engine and both went over 200K miles with very few problems.
One popped a plug out at 170K miles, it was a $250 fix at the dealer.
Used to get 14-18 mpg with them, better than my current 6.0L Chevy.