WICHITA - A southwestern Kansas packing plant is being sued by workers alleging they're short-changed on wages and overtime pay. The lawsuit was filed Tuesday in federal court on behalf of 2,000 workers at National Beef Packing's plant in Liberal. It challenges the practice of paying hourly meat-processing workers based on so-called "gang time," which pays only for the time the production line is running. The suit seeks class-action status.  Similar lawsuits were filed last year against Creekstone Farms Premium Beef in Arkansas City and last month against the Farmland Foods slaughterhouse in Illinois.