I saw a used Titan on the stealership lot with a fifth wheel in the bed when I was shopping for my Titan. I know it can be done. Also check JCWhitney.com. I have the mag in front of me now, they have fifth wheel hitches, there is a 16K lb. slider kit fifth wheel part number MU514790FE for $599 and there is a gooseneck hitch that mounts onto fifth wheel rails with a 25k lb. capacity part # MU514681 for $199. The gooseneck will fit 6 and 8ft. beds, the 16k LB. slider says it fits long and short bed pickups, it has a 12" slider on it. Hope that helps a little.
:google:
:google: