What is it you are wanting to accomplish? To get lower RPM at highway speeds? To save gas consumption? You should have my setup. A 3.89 rear end that is doing more like 3200 RPM at 60. Gas Mileage? Forget that question. I agree with the statement that what you would save in RPM is not going to justify the cost and hassel of swapping out the rear end. Bet you wouldn't even notice it. I am pondering swapping out my 4 speed for a 5 or 6 speed to get a highway gear. I hate to lose my Toploader though. I'd be looking for a newer AOD transmission. That makes more sense to me. A 2.80 rear gear? Most of us owners want a lower gear for acceleration.