You can contact Briggs & Stratton for all of the manuals and parts list that you need.
Briggs & Stratton
Vanguard 18 hp, Air Cooled, gasoline engine.
Engine: Briggs & Stratton 18hp Vanguard engine, Twin Cylinder, Hour meter, Electric Start with battery storage box, 10 gallon fuel tank. (Battery not included)
Engine: Vanguard 21 hp, Air Cooled, gasoline engine.