IMO, unless you will be towing >5,000 lbs much of the time or for long distances occasionally, the 3.55's will be just fine, even with 33's.

You have to keep in mind that the 6-speed has some very low gears (1: 4.17, 2: 2.34, 3: 1.52, 4: 1.14, 5: 0.87, 6: 0.69) and you have the ability to lock out O/D so you should be able to keep the engine at or near peak torque for most of your driving needs.