[wingnut60]

Adding air bags to a suspension that is already too stiff for the load doesn't make sense to me. Or did I mis-understand what you are saying?
As Jim said, the C/C units of RAM and Ford are de-rated to keep multiple drivers from flogging the units...you will be disappointed with the performance of the de-tuned vs the regular models. Friend of mine with commercial units has gone to getting the pickups and pulling the beds to put flatbeds on them to get the more powerful engines.
And you definitely don't need the 5500 to pull a 37' fiver...
Another thought--most C/C units don't get the highest trim levels if that is what you would be wanting.