This subpart applies to manufacturers of passenger cars, multipurpose passenger vehicles, trucks, and buses with a GVWR of 3,855 kg (8,500 pounds) or less and an unloaded vehicle weight of 2,495 kg (5,500 pounds) or less, except for walk-in van-type trucks or vehicles designed to be sold exclusively to the U.S. Postal Service, for which part 563 applies. However, this subpart does not apply to vehicles excluded by § 563.3 from the requirements of that standard.