Should be standard, mine were. I just traded in a '06 Dodge dually for a new 2015 RAM. The '06 had a 16k Draw Tight slider in it when we bought it, which we used until last spring when we bought our Suites. I had to up-grade the Draw Tight to something more substantial, ended up buying a Reese 20k hitch off of Craig's list. I called a local shop to make sure the Reese would fit the rails and they told me "should be standard". They were right, the Reese dropped right in!
Now I have the 2015 RAM with the factory fifth wheel prep package so I decided to go with a brand new B & W 25k that drops into the factory puck system.
Dan