The sport and r/t rams come with muffler 52122529AC.
Express, Laramie, Big Horn come with muffler 55398327AG.
I had a 2014 express and bought an oem muffler off of a sport and swapped onto the express. They look exactly alike on the outside. The sport/ r/t muffler is chambered different and is listed as deep exhaust note on the build sheet. I really liked the way it sounded, really quite at cruise, no drone, but roared better at WOT and cold start up.
If you search the sport part number you can actually find some pics on the other forums where they had cut open a sport muffler and you could see the difference.