Website says to just lay a piece of plywood on top of it and load 'er up. And I did buy a new set of snow tires last fall, made a huge difference. But an empty truck still benefits from some weight.
One year in NY, I strapped down two 55 gal drums in the back of my '72 2wd Chevy C-10 and filled them with water. That sumbitch would go anywhere after that.