Just bought a new Keystone Cougar! What else do I need?

At over 9000 pounds and more than 31 feet long your really pushing your luck with a 150. The numbers you cited are advertised dry weights not anywherw close to the weighta you will see when,loaded ready to travel. Also please remember everything you add to the truck beyond a stripped teuck with one 150 pound driver reduces your trucks actual towing capacity.