I have towed a 42 OL from Rhode Island to Miami with my 02 2500 Duramax 4x4, did it fine, but that is because we were out of bigger trucks. I would say it can be done, but deffinately not for everybody.
The boat get's sucked in towards passing trailer trucks and even jersey barriers, and the sudden latteral movement of the boat makes the rear of the truck seem squirley, where the dually's and / or f-650's don't move.
I think you will be within load limits, depending on your vin #, but you have to drive the truck throught he crosswinds twice as hard as you would with a bigger truck.
I never had any breaking issues, but most boat trailers brakes work about 50% of the time, and I wouldn't want to try that weight on the small gm breaks on the 2500.
No question that the 06 Duramax and 6 speed allison will have the sack, but that is only half the battle.
Call a proffesional, especially with the cat, they will have all the permits available and know all of the routes that are better suited for the extra width. Call Joy at powerboat concierge service, she is the best.