Gross rear axle weight rating (at least on the 2018 1500s) is 3,950 lbs. Looks like most of the tires available in the stock 255/70R17 size are S rated which a quick glance shows are good for ~2,400 lbs a piece, so, you would be okay with S rated tires but stepping up to an E rated (3,200 lbs capacity) would give you a bit more margin.Chevy Silverado 1500