Are you looking for new or used?
If new, then you will get all of the benefits and improvements made through the last ten years. If buying used, then look for a 2006 MY chassis or newer. That is when the 3-valve V-10 was introduced, and just before that the five-speed TorqShift transmission. In 2016 they introduced the six-speed TorqShift. From reading here, i get the impression that those with the five speed get the most benefit from a 5Star tune. It seems to really make the powertrain shine once loaded. I have a 2006, with the Gale Banks Power Pack, Ram Air Intake System and the Otto-Mind tune. It does pretty well, but of course it's only a 29 footer.
You might also want to ask your state DMV if their restrictions are for GVWR or GCWR. That could make a difference for some larger gassers.