Gear Vendors for Excursion V-10 4.30 rear

I doubt my truck is worth $5,000. The issue is what it is worth to have a more satisfactory tow experience. Last tow I put in noise isolating earbuds so the noise of the motor revving didn't bother me as much. That is obviously the cheapest solution. The most expensive solution is to buy a used diesel truck. This solution is significantly cheaper if it works. Used diesels are expensive to purchase and maintain. I may recoup $300 in fuel savings a year, but the truck probably won't last long enough for a full payback. However, it will last long enough for a partial payback. So if the cost is $3,500, is it worth $1,700 for a better towing experience? I need to think about it. When it revs, it will maintain a reasonable speed. There is just something about it that bothers me. Lets give the earbuds another shot on this summer's trip.

I don't suppose there is a 6 speed transmission that would bolt in, is there? I've got 100,000 on this transmission.