Worry about your payload capacity not your manufacturers tow rating. If the sub can carry it, it can tow it. If you don't like how it tows with the 3.73 from a power prespective then switching to 4.10s will improve towing power but it does nothing for payload capacity.
The big hint here is: With an SUV and TT with all the stuff and people most carry with them you will run out of payload capacity/axle capacity long before you hit the manufacturers tow rating. Should be less of a problem with a 3/4 ton SUV but will still be true with passengers and gear.