Here is a couple of videos of my truck and the exhaust I put on recently. I ran 2.25" pipe from where the cats where to (2) Thrush welded 2.5" mufflers and 2.5" on out to the sides turned down.
https://youtu.be/AUa5NLlas2o
https://youtu.be/E5vtjK5zyq4
I picked this truck up last week and really like it so far. I will probably do exhaust soon since it still has the stock on it. Also looking for the nnbs LTZ 18" wheels.