Hey, ya the owners of the 5500 are pretty rare around here. Those are some pretty serious rigs. The best I can do is you could post in the 4th gen cummins diesel specific section here. There is also this other cummins section here. I know it isn't much, but I wish I could be of more assistance to you. If I get more knowledge I will be sure to let you know.
Looks like there are few if any RAM 4500/5500 owners on here. I purchased the 5500 for the heavier running gear and the high tow rating. We need to tow tractors, implements and hay bales on a 30,000 lbs. rated gooseneck. Serious business and I hate breakdowns. That's the reason for needing the heavier tires, wheels and brakes.
We don't need the high tow ratings every day but when the need arises we can't afford to skimp. Mostly the truck will be used for running about, thus we went with the Laramie.
If there are any C&C owners hanging about I sure would like to compare notes.
I did have some interesting experiences during the process of ordering a new vehicle and I can give some insight on dealing with ISG services.