I just checked the Fit Guide on Reeses website and found that your existing hitch is not compatable with the new truck. They do not make the underbed rails for your hitch.
If you have the Ram fifth wheel prep package then I would order a B&W RVK3600 or if you are happy with the Reese products they make one that fit the pucks. I think the part number is 30160.
If you do not have the Ram pucks then you have a few options for underbed rails.
1) You can install a B&W Turnover ball Gooseneck hitch and use the B&W Companion hitch
2) You can install any brand underbed gooseneck hitch and use a hitch called the Andersen Ultimate fifth wheel connection (not my personal preference)
Or you can install standard fifth wheel hitch above bed rails and run a traditional rail mounted fifth wheel hitch. I still recommend the B&W brand called the Patriot. I would buy the 18k version which has a welded base.
My personal favorite combo without the factory Prep package is the B&W Turnoverball and the Companion fifth wheel hitch.
Sorry for the bad news on your current hitch. You can probably get $2-400 for it on craigslist to help offset the cost.
Thanks!
Jeremiah