I drove a 2000 Dakota for eight years and really liked it. Mine was the 4.7 liter V8 and automatic transmission, limited slip rear axle, full-time four wheel drive. Its limiting factor was ground clearance, not traction. I had about 300 pounds of extra weight over the rear axle and believe that helped a great deal with rear-wheel traction.
Are you getting stuck frequently? Is it due to a lack of traction? If the answer is yes, then locking diffs will help. If no, then you might consider spending that money on something else.