The 700R4 was noted rated to TOW in overdrive so I put a Gear vendors splitter behind it set over and towed in 3rd. over.
I would suggest considering the 400, stronger trans, with a splitter behind it. That will give you 5 usable forward gears. 1sr, 2nd, 2ndover, 3rd, and 3rd over.
If you really want a neat setup put a BD Torq Loc in and lock the convertor in any gear over 35 mph. Pulling long hills in 2nd over with the convertor locked at 55 or better.
WBCCI 12156 AIR 3144 WACHUNG TAC NJ6
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles