hitch balls go up to 3 inches and larger.
The ball may go that big, but you need a mounting platform to support accelerating and stopping that weight. Class IV receiver hitch is not going to do it.
You are probably talking about a mobile home type mover. Or some similar rated equipment.
Class V hitches top out at 18,000 lbs. These are the type used for 2.5 & 3 inch balls.
http://www.etrailer.com/faq-hitchclasses.aspx
Those are big balls.