The GMC K25 Suburban headlight bulb specifications include H6024 and H5001 sizes for high beam applications, along with H6024 and H5006 sizes for low beam functions. The replacement chart covers 1967 through 1978 model years with corresponding bulb size data.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The GMC K25 Suburban uses three distinct sealed beam unit types across its 1967-1978 model range: H6024, H5001, and H5006, all operating at 12V and conforming to ANSI standards recognized in both the United States and Canada.
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 requires replacement rather than an internal bulb swap.
The H6024 is a 7-inch round sealed beam unit. On the GMC K25 Suburban, it serves as both the high beam and low beam headlight for the 1973-1978 model years, functioning as a dual-purpose unit within a single-lamp system.
The H5001 is a 4-inch square sealed beam unit designated for high beam use on the K25 Suburban for model years 1967-1972. Its square form factor is physically distinct from the round units used in other positions and years, making cross-substitution between these types impossible.
The H5006 is a 5.75-inch round sealed beam unit used exclusively for the low beam position on the 1967-1972 K25 Suburban. Although it shares a round form with the H6024, the two differ in physical size and are not interchangeable.
The 1967-1972 K25 Suburban used a four-headlight configuration, with the H5001 handling high beams and the H5006 handling low beams as separate units. The 1973-1978 model years transitioned to the H6024 for both functions, indicating a shift to a two-headlight system.
Because the H5001 and H5006 differ in both shape and size, fitment between the two positions on 1967-1972 models is not possible, even though both units belong to the same ANSI-standardized sealed beam family.
The H6024 and H5006 are both round sealed beam units but are sized differently at 7 inches and 5.75 inches respectively, which means they occupy different mounting housings and are not substitutable for one another despite their shared round profile.