GMC G1000 Series headlight bulbs utilize H5001 and H6024 sizes for high beam applications and H5006 and H6024 sizes for low beam functions. The replacement chart covers 1963 through 1966 model years with corresponding bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The GMC G1000 Series headlight specifications reference three sealed beam unit types across all listed model years: H5001, H6024, and H5006. All three conform to ANSI standards applicable in both the United States and Canada and operate on 12V electrical systems.
All three bulb types are sealed beam units, meaning the lens, reflector, and filament are fused into a single assembly. When a filament fails, the entire unit is replaced rather than an internal bulb component.
The H6024 is a 7-inch round sealed beam unit and serves as both the high beam and low beam source on GMC G1000 Series vehicles equipped with a 2-headlamp configuration for model years 1963-1965. A single bulb type handling both functions is characteristic of a 2-lamp system, where each unit contains dual filaments.
The H5001 is a 4-inch square sealed beam unit designated exclusively for the high beam position on vehicles with a 4-headlamp configuration, covering model years 1963-1965, and also serves as the sole high beam unit for the 1966 model year regardless of headlamp count.
The H5006 is a 5.75-inch round sealed beam unit assigned to the low beam position on 4-headlamp configurations for model years 1963-1965, and is also the designated low beam unit for the 1966 model year.
The GMC G1000 Series (1963-1965) presents a headlamp configuration dependency that directly affects bulb selection. The 2-headlamp arrangement uses H6024 units for both beam functions, while the 4-headlamp arrangement splits the roles between H5001 for high beam and H5006 for low beam. Substituting one configuration's bulb into the other is not supported by these specifications.
The 1966 model year does not carry a headlamp count qualifier in the specifications, with H5001 listed for high beam and H5006 for low beam, indicating a 4-headlamp arrangement as the applicable configuration for that year.
The physical formats across the three bulb types are distinct: the H5001 is square while the H6024 and H5006 are round, and all three differ in size. These physical differences make the units non-interchangeable despite sharing the same ANSI standard framework and voltage rating.