Not much available for the '16s yet. Pretty normal for new vehicles of all types, IMHO.
There is one intake available for the 6.4L, at least the last time I checked, from K&N. Limited availability from what I can see.
Exhaust is pretty much what you wanna do unless you have the self leveling rear air suspension. With that you are limited to a single in/single out muffler as there is no room to run anything over to the other side. What I did was to use a Magnaflow muffler and got rid of the resonator.
In your case any good exhaust shop can make up just about anything you want. Last time I checked there was one catback available for the 6.4L engined trucks and it was uber expensive.
Good luck with the mods.