I pull a 2015 Jayco Seismic (dry weight of about 15K). I had a Dodge 2500 with firestone airbags, a Banks exhaust brake with the 5.9 Cummins. I had no problems pulling in OK, AR, TN, etc. However, Monarch Pass did the 2500 in! It got us home, but the tranny was shot. I loved this truck, but the tranny could not pull my heavy girl in the mountains.
I got home, and traded for a 2015 RAM 5500. Put a CM flatbed on it and B&W flatbed Companion hitch. The truck has the Aisin 6 speed tranny and I got 4.88 gears. My world is totally different now! Love this truck and feel much safer pulling with it. Pulls that 44ft fifth wheel like its a little wagon.
When I began the fifth wheel buying journey, I thought I could modify my undersized pickup and be okay. I was dead wrong. Get a tow vehicle that is more than you'll need. There is nothing more stressfull than having all your kids, two dogs, and gear on a trip. Then praying you'll make it home. I had to learn the hard way....