The Megacabs came out in 2006. Before that just quadcabs. If you are hauling people go with the Mega. I just sold my 06 QC & bought a MC. The kids just didn't have enough room in the QC to be comfortable in the QC. As far as gearing the 3:73's will pull just fine unless you are adding big tires etc.

 

You could only get the 305HP/555TQ in a 6 speed in 2003. The autos were 250HP SO (not HO) and the 47RE auto that wasn't up to the power. A few SO's had the 48RE as I just learned lately in posts here. Also, the lift pump was remote from the tank in 03 and a TSB put it in the tank. Some are done, some are not. (lift pump discussion on here will take a week or so alone )

The manual seems to be more durable and probably best for towing. A lot of folks upgrade their autos. Probably not an issue with normal use. Mods, big loads and abuse suggest an upgrade is in order.

The front end is the weakest point and will cost you if you don't do most of your own work. Off road will increase these failures, on street, not so much.

The best part is you get a Cummins!! Welcome.

Cya