Trailer Life magazine puts out a nice towing guide every year that has specifics for the various makes/models as well as just some good towing knowledge (explaining some of the measures, etc.). You can find them at this link. Figure the 2013 guide should be out soon, probably when Ram finally releases their 2013 numbers. Here you go:
http://www.trailerlife.com/trailer-towing-guides/
Over the past 10 years I have had trucks of all three major brands - Chevy/GMC, Dodge, and Ford. My current TV is a 2012 F350 CC DRW and I love it. My dodges were good trucks, but lower on the power end We have a Cyclone 4100 King at 18,000 pounds and if you have something similar either the Ford DRW and Ram DRW will get it done for you, no issues. You'll probably have at least one person tell you that you need a F450 for a trailer that size, but you are well within all specifications and safety designs on both the Ford and Dodge, up to even a 21,000 pound coach. You do likely need the DRW versus SRW though.
Happy purchasing - I love shopping for trucks (as you can probably tell).