Will be trading to a 5th Wheel. Which TV. (F350 or Ram 3500)

Don't know about capacity's, though I did own an 05 Chevy 3500 CC/LB/4X4/ dually in LTZ trim, equipped with the LLY Duramax...was a good truck, though some LLY's were prone to some over heating issues, mine was fine...I towed a Coachmen Somerset with a 14,500# GVW and no issues towing...

Don't know about the 5.9, but do think the 6.0 diesel in the Ford is one you might want to steer clear of from all I've read about that particular diesel engine, though some have reported no issues...