Biggest issue is do you already have phone/VR buttons on the steering wheel with BT Connectivity & mics in the headliner? If yes ....
Then I recommend you stick with a 2018 radio to avoid cell system error messages that happen with using an earlier radio (correct USA Ram radio PNs are listed in op).
The 4 speed 8.4 HVAC conversion harness/process is the same as the 13-17 trucks other than using the 2018 2500 68366553AA HVAC module and likely needing to add Auto Temp Control (ATC) feature & cabin sensor for Temp blend door to have full travel/work correctly.
To get the bu camera to display on the radio, you'd also need a backup cam reroute harness.
See the first 5-6 posts for relevant links/threads.
If you don't have the mics ....
I usually recommend swappping out the mirror and it's harness for one from a 13-16 truck that has the mics (& AutoDim usually) and adding the mic reroute wiring into the camera reroute harness.
I may be able to make a mic only add-on harness for the headliner, but you'd need to get the PNs for the 2 mics, pull the headliner down at the front and cut out the openings to install them. It would be a one off harness without any written install info/pictures until sometime is willing to go this route.
M² Mods.