The pin weight of a 34' Challenger is probably more than the payload capacity of his 2500. It certainly would overload my 2005 D'Max. A 2000 Citation 35 footer put me WAY over.
Re-arching springs and adding Timbrens (if he can stand the harsh ride they create) may help but it is simply masking the problem.
Bottom line - probably too much trailer for that truck.
Not what you want to hear, but you should probably run the numbers to check.
Later (2011 and up) 3/4 tons can probably handle it, but the older ones, especially diesels, were low on payload capacity.
