The 2013-2018 Ram 3500 heavy duty trucks have 4 basic different suspensions that come into play when selecting a lift kit; Diesel or Gas engine, and with or without rear air overload system. So basically it breaks down to Diesel without rear air, Diesel with rear air, Gas without rear air and Gas with rear air.
The first two choices are between the Diesel engine and the Gas engine. The basic lifts are the same but they require different front coil springs which will affect the amount of lift that you get. Be sure to select the proper kit so that you get the right amount of lift. The 2 inch levelling kits do not replace the front coil springs so those kits will fit both gas and diesel models.
The second big difference is in the rear suspension, these trucks are available with an auto-leveling rear airbag option, You need to know if your truck has this option in order to get the proper parts for the rear of your Ram 3500 lift kit. Once again, if you just want a levelling kit then there is no rear lift so there is only one listing.