GMC 370 high beam and low beam headlight bulbs utilize H6024, H5001, H6006, and H5006 bulb sizes across different model configurations. The replacement chart covers vehicle production years spanning 1951 to 1959 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 H6006 is the most frequently specified bulb across the GMC 370's headlight fitments, covering both high and low beam positions for the 1951-1955 model years. It is a 5x7-inch rectangular sealed beam unit rated at 12V and built to the ANSI standard applicable in the US and Canada.
The H6024 is a 7-inch round sealed beam unit operating at 12V under the same ANSI standard. It serves both the high and low beam positions on the GMC 370 for the 1956-1957 model years, and also on 1958-1959 vehicles equipped with a two-headlamp configuration.
All four bulb types listed in these specifications, H6006, H6024, H5001, and H5006, are sealed beam units. In a sealed beam design, the lens, reflector, and filament are fused into a single glass assembly, meaning the entire unit is replaced rather than an individual bulb.
The 1958-1959 GMC 370 introduced a four-headlamp configuration as an alternative to the two-headlamp setup, which required two distinct bulb types to be used together. The H5001, a 4-inch square sealed beam unit, handled the high beam function, while the H5006, a 5.75-inch round sealed beam unit, handled the low beam function.
The H5001 and H5006 are not interchangeable with the H6024, despite all three being 12V ANSI-standard sealed beam units. Each has a different physical form factor, and the four-headlamp system they serve is a separate headlamp arrangement from the two-headlamp system that uses the H6024.
The transition from H6006 to H6024 between the 1955 and 1956 model years represents a change in sealed beam form factor, from a 5x7-inch rectangular unit to a 7-inch round unit, while the operating voltage and ANSI compliance remained the same.