To dual or not to dual, what should I dual?

[DBelshee]

I am one lucky guy who gets to order a new Dodge! Now, I need the opinion of experts! We are ordering a 3500 with the new Cummins and 6 speed, and plan on pulling a 5th wheel with gvw of around 14000#. Now that there is a choice of a single or dual rear tire, what do I really need? I'm sure that if I had a large camper, the dually would be the way to go. The pin weight on the 5th is around 2400#, and I can't see packing around two extra tires on the back of the truck, unless I need to for stability reasons, etc. Any input? Also, what about the rear gear ratio? Pulling a GVCW of around 21000#, is the 3.73 ratio acceptable, or do I need the 4.10? Thirdly, have any of you had any experience with exhaust brakes? What brands do you use, and what are the pros and cons to each one, and why did you choose a particular brand? Lastly, for those of you pulling fifth wheels, are you using 2 or 4x4's? Do the 4x4's raise the 5th wheels so high that it makes it handle poorly, and, do the 2 wheelers have enough traction in less than ideal road conditions such as mountainous gravel roads, etc? I've had 2 wheel drive pickups before that have gotten stuck on wet grass, but have never pulled a 5th wheel behind a 2 wheel pickup. Any ideas? And finally, are there any options which you have found you could'nt do without? Thank you in advance for all of your input! You guys and the TDR are simply awesome! Keep up the good work!