The GMC 1000 Series 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 documents bulb size data spanning 1960 to 1965 production years.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The GMC 1000 Series (1960-1965) uses three sealed beam bulb types across its headlamp configurations: H6024, H5001, and H5006. All three conform to ANSI standards applicable in the United States and Canada and operate on a 12V electrical system.
Sealed beam units integrate the filament, reflector, and lens into a single housing. None of the three bulb types used in this application accept a replaceable internal bulb; the entire sealed unit is replaced when a failure occurs.
The H6024 is a 7-inch round sealed beam unit. It serves as both the high beam and low beam source in the two-headlamp configuration of the GMC 1000 Series (1960-1965), meaning a single unit type handles both functions in that setup.
The four-headlamp configuration divides high and low beam duties between two distinct sealed beam types. The H5001, a 4-inch square unit, is designated for high beam use, while the H5006, a 5.75-inch round unit, handles low beam output.
The H5001 and H5006 are not interchangeable with each other despite both being used in the four-headlamp system. Their physical form factors differ, with one being square and the other round, and their beam functions are separate.
The H6024 used in the two-headlamp system is physically and functionally distinct from both the H5001 and H5006 used in the four-headlamp system. Substituting across these configurations is not supported by the specifications.
The bulb fitment for the GMC 1000 Series remains consistent across all six model years covered, from 1960 through 1965, with no variation in bulb type assignments for either the two-headlamp or four-headlamp configurations.
The headlamp configuration present on a given vehicle, either two-headlamp or four-headlamp, is the determining factor for which bulb types apply. The same model year carries different bulb requirements depending on which configuration is installed.