GMC S300 headlight bulbs utilize H6024 and H6006 sizes for both high and low beam applications, with these bulb designations representing the specific specifications required for this model. The replacement chart covers 1955 to 1957 production years and details the bulb size requirements across the vehicle's manufacturing span.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The GMC S300 uses two distinct sealed beam types across its model years: the H6024, a 7-inch round unit, and the H6006, a 5x7-inch rectangular unit. Both conform to ANSI standards recognized in the United States and Canada and operate on a 12-volt system.
Sealed beam units are self-contained assemblies in which the filament, reflector, and lens are fused into a single housing. When a sealed beam fails, the entire unit is replaced rather than an internal bulb.
The H6024 applies to the 1956-1957 model years for both high beam and low beam functions. The round format of this unit was a common configuration in mid-century American vehicle lighting.
The 1955 GMC S300 uses the H6006 for both high beam and low beam positions. The rectangular profile of the H6006 distinguishes it physically from the H6024 and makes the two units non-interchangeable despite sharing the same 12-volt rating.
Because the H6024 is round and the H6006 is rectangular, substituting one for the other is not possible without modification to the housing. The physical formats are incompatible regardless of shared electrical characteristics.
Both sealed beam types carry ANSI standardization, meaning units from different manufacturers that share the same designation conform to the same physical and electrical specifications and are interchangeable with one another within that designation.