I did this a while back and there are threads on this subject sprinkled around the forum so far as the settings you'll need the change with AlfaOBD. If the parts are still hard to come by you might be checking ebay regularly until you can get your hands on all of them.
@Jimmy07 can build you the harnesses you'll need (where I got mine) and I used the following parts in my ram :
12"/8.4" w/NAV Module - 68507350AF
12" Screen - 68526609AC
The Bezel for my black Laramie (will vary based on your truck interior) - 6EZ155X9AE
To mount the module to the inside of the dash behind the screen you'll also want to get a license plate mounting kit with the square plastic or metal inserts if your truck doesn't have the nut inserts present from the factory (mine did not). You will also need some machine screws to mount the screen to the bezel, I honestly can't remember the size as I keep a ton of machine screws on hand in various sizes.