GMC G1500 Headlight Bulb Size

Additional Notes

• The H6054 sealed beam unit is the most frequently specified bulb across the GMC G1500 headlight data, appearing in both high beam and low beam positions across the 2-headlamp configuration for model years 1979-1995, as well as the 2-rectangular-headlamp variant in 1980 and the single-configuration years 1981-1984. It is a 5x7-inch rectangular sealed beam unit operating at 12V under the ANSI standard applicable to the US and Canada.
• All bulb types listed in the GMC G1500 specifications are sealed beam units, meaning the entire lens, reflector, and filament assembly is replaced as one piece rather than a separate replaceable bulb being fitted into a housing. This applies uniformly across every position and model year in the data.
• The H6024 is a 7-inch round sealed beam unit and serves as the specified bulb for both high and low beam in the 2-headlamp configuration for 1964-1965, the single-configuration years 1985-1987, and the 2-round-headlamp variant in 1980. It operates at 12V and conforms to the ANSI standard for the US and Canada.
• The 4-headlamp configuration on the G1500 introduces beam-function separation, where distinct bulb types handle high and low beam duties independently. For 1992-1995, the H4701 handles high beam and the H4703 handles low beam, both being 7-inch round sealed beam units at 12V, though they are not interchangeable with each other due to differing beam optics.
• The 4-headlamp configuration for 1988-1991 uses 4x6-inch rectangular sealed beam units rather than the 7-inch round units found in later years. The H4651 and H4652 are specified for high and low beam respectively in 1990-1991, while 1989 pairs the H4651 for high beam with the H4656 for low beam, and 1988 uses the same H4651 and H4652 pairing as 1990-1991.
• The H4652 is described as a variant of the H4651, both being 4x6-inch rectangular sealed beam units at 12V. Despite their physical similarity, they serve different beam functions and are not listed as interchangeable within the specifications.
• The H5001 and H5006 are specified exclusively for the 4-headlamp configurations in 1964-1966. The H5001 is a 4-inch square sealed beam unit assigned to the high beam position, while the H5006 is a 5.75-inch round sealed beam unit assigned to the low beam position. Both operate at 12V under the ANSI standard.
• The 1980 model year is the only year in the specifications where two distinct headlamp configurations are differentiated by physical shape within the same headlamp count, with the 2-rectangular-headlamp variant using the H6054 and the 2-round-headlamp variant using the H6024. These two units are not interchangeable due to their differing form factors.