I don't have any trouble towing, but would like a better towing experience and I might go bigger some day . As far as mpg goes I only use the truck for recreation and towing so it doesn't matter. I am not looking for a return on the money just more performance . I will probably do it as it seems it will " wake up " the v10 . For the gas I burn I don't feel the performance is there with the 3:73. As for the 5.4 with the 3:73s I had that with my 98 expedition and towed a 5k hybrid and it was just OK , I can't even imagine towing 7200k with it on the hills. I don't tow over 55 so it's not about speed. Thanks to everyone for the input! I will try and update this thread next spring with the results!