We traveled the other direction 2 years ago with the RAM 1500 with 5.7L v8 Gas w/air suspension and 34' TT (not 5th wheel). I can't remember anything particularly concerning or problematic. I'm vigilant about using the transmission to slow down on downhills and keep my foot off the brake as much as possible, never riding them occasionally stabbing them to slow down if necessary.
Hopefully goes without saying, but fwiw take into account how much "stuff" you're picking up and where its placed in the truck and fifth wheel. Weight and balance can make a huge difference.
