Any 5th wheels that fit ‘18 2500 6 ft bed w/vertical aux tank

[Popz24Boyz]

I do a lot of long distance towing/hauling, so I recently purchased and am installing this weekend a 90 gal RDS aux fuel tank. My issue is that I am being told a 5th wheel hitch will not fit in the bed with the tank because of rails? I have never dealt with 5th wheel hitches and the older gentleman at my local camping world didn’t seem very much enthused to help. So please, any advice or information would very much appreciated.