At stock height, the tires clear the rear fenders. The box inner fenders overhangs the frame by 3"-4" on each side, the factory wheel wells are about 12" wide. The track width of a Dakota is about 60", but the factory wheels have a lot of backspacing. The factory rear axle is either a 7 1/4 or an 8 1/4".
If you want to deal with a narrow rear end, pro-street an 87-96 Dakota would be pretty easy. Move the inner fender back to the frame, fill the gap, mount up the narrow rear axle, (or get the proper backspacing on the wheels), and put on the meats. Gene