Anyone towing a fifth wheel with Dodge 2500 6.4 Hemi 4x4?

The first thing other than bed height you need to look at is payload. Look at your sticker in door jamb. The amount of weight the truck can carry as it left factory will tell you a lot. The loaded pin of any fifth wheel rv you choose will weigh around 20 percent of the fifth wheel gvwr. If you want to tow fiver, you should consider pin weight first then consider putting stock tires/wheels on the truck. With a 3/4 ton gasser especially with 3:73 axle I would keep fifth wheel gvwr at 10k or less.