2014 2500 HD Chev.

reddog7571 wrote:
How big of a 5th wheel will this unit tow safely??

Truck payload rating and pin weight is the deciding factor. Also depends on which 2500 and what the yellow sticker in the door jamb says the truck can carry. In a crew cab 4x4 my guess is stick with a fifth wheel with 11,000 gvwr or less.
Like others said, you should weigh the truck loaded as if going camping and add 250 lbs for hitch. The remaining balance of available payload is what you have to work with for pin weight.
I've been down this road and is why I have a 3500 to tow my 12k lb fifth wheel (has 2400 lb pin loaded).