Dry and Orcutt introduced the Model III King Midget in 1957. The basic body design of this model was used through the end of production. Other significant changes included unit body construction, with the frame and all fixed body components welded together for strength, four wheel hydraulic brakes, and 9.2 horsepower.

As time progressed, other improvements evolved. The Philippine mahogany doors were replaced by aluminum doors and, near the end, steel doors. The electrical system was upgraded from 6 to 12 volts in 1961. The old standby Wisconsin AENL engine was replaced by a 12 horsepower Kohler K301 engine in 1966. The clicker low speed pulley was replaced by a silent Borg-Warner one-way clutch in 1967. The brown canvas top was replaced by a vinyl covered black or white top. An optional electric windshield wiper was offered, along with a windshield washer, radio, carpeted panels, floor mats, safety belts and new paint colors: Corinthian white, Rangoon red, yellow, blue and aqua.