You can get the air suspension if you order the diesel, max tow package and dual rear wheels. It is included in the Max Tow Package and you must have the dual rear wheels.
Ram is really blowing it on some of this. Some bean counter is disenfranchising a lot of buyers. I want a Big Horn and MegaCab. Can't get any more. I want air suspension like you, but I do NOT want a dually. So frustrating. I have NO INTEREST in painted bumpers. Guess what? They made them STANDARD. Now you have to pay extra for chrome. The thing is, the person ordering the truck is too lazy to check that box. So many otherwise perfect trucks for me sitting on the dealership lot do not have chrome bumpers. Double frustrating.....