Just for a test, put 100 pounds in the bed near the tailgate.
I have a '50 1/2 ton which smooths out incredibly when I tow my boat behind it. I need to put a set of scales on the boat trailer tongue to figure out what I need to add to the rear of the truck when not towing the boat. Rather than putting the weight in the bed I might come up with a way to attach something of that weight where the spare tire used to go which would be easily removable.
