I have the AirRide Technologies kit of the front of my truck. Its a decent kit, but it requires you to cut a significant amount of metal out of the frame, where the coils go, for clearance for the bags. If you cut the fender wells out and make a little knotch for the control arms your truck will lay on the crossmember with this kit.
In the rear of new gen dakota's you have to narrow the rear end to lay it down low. I have 245/45/17's on R/T wheels with a 7" drop and the rear tires are CONSTANTLY rubbing on the lips. Unless you get pretty crazy offset, if you want to go really low I would deffinately reccomend narrowing the rear end.