Long Bed or Short Bed PU for towing a fifth wheel?

We are getting ready to purchase a 1 ton Dodge or GMC Denali PU to pull an overall length fifth wheel of 37 feet. Could we get some opinions on whether to go with a long bed PU (8 foot)or a short bed (6 1/2 foot). We are planning on being fulltime RVers for a couple of years.