GMC 3500 high beam headlight bulbs use H5001 or H6024 size, while low beam headlight bulbs use H5006 or H6024 size. The replacement chart covers 1960 to 1966 production 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 3500 headlight specifications for 1960-1966 reference three sealed beam bulb types: H5001, H6024, and H5006. All three conform to ANSI standards recognized in both the United States and Canada, and all operate at 12 volts.
Sealed beam units integrate the filament, reflector, and lens into a single assembly. None of the three bulb types listed accept a replaceable internal bulb; the entire sealed unit is replaced when the light fails.
The H6024 is a 7-inch round sealed beam unit. It appears across the 1960-1965 model years as both the high beam and low beam bulb on GMC 3500 vehicles equipped with a 2-headlamp configuration.
The H5001 is a 4-inch square sealed beam unit designated for high beam use. It is specified for 4-headlamp configurations across the 1960-1965 model years, and it is the sole high beam bulb listed for the 1966 model year regardless of headlamp count.
The H5006 is a 5.75-inch round sealed beam unit designated for low beam use. It serves 4-headlamp configurations across the 1960-1965 model years and is the sole low beam bulb listed for 1966.
The 2-headlamp and 4-headlamp configurations on the GMC 3500 (1960-1965) use entirely different bulb types. The 2-headlamp setup uses the H6024 for both high and low beam functions, while the 4-headlamp setup splits those functions between the H5001 and H5006 respectively.
Because the H6024, H5001, and H5006 differ in physical form, a round 7-inch unit cannot substitute for a square 4-inch unit or a round 5.75-inch unit. The housing configuration of the vehicle determines which sealed beam type is physically compatible.
The 1966 model year does not carry a headlamp count condition in its specifications, with the H5001 listed for high beam and the H5006 listed for low beam as single entries without qualifier.