Be careful with 2015.
there were exhaust fluid issues with those.
Mine got lemon law by-back. What a pain in the ass that truck was. I was in limp-mode(22mph tops) 2x on desert center.
Good luck with your search Sir. I've somewhat been looking at these as well, and the pricing is through the roof. Found one (I think Glendora), at a small used car lot, but can't remember the name off hand.
Just sold my '19 for more then I paid for it and put on 27,000 miles its stupid what is going on with used boats, trailers, SxS, and now diesel trucks....
Knowing many people who have had the CP4 pump fail on the LML (11-16) I would stick with the L5P (17 and Up). I have a 2019 GMC dually with 23000 miles on it and have had no issues with it.