GMC 150 high beam and low beam headlight bulbs utilize H6024, H5001, H6006, and H5006 bulb sizes depending on configuration. The replacement chart covers 1951 through 1959 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 H6006 is the most consistently specified sealed beam unit across the GMC 150's headlight history, covering both high and low beam positions from 1951-1955. It is a 5x7-inch rectangular sealed beam unit rated at 12V and conforms to ANSI standards applicable in the US and Canada.
All four bulb types listed for the GMC 150, namely H6024, H5001, H6006, and H5006, are sealed beam units. In sealed beam construction, the reflector, lens, and filament are fused into a single glass housing, meaning the entire unit is replaced rather than an individual bulb.
The H6024 is a 7-inch round sealed beam unit operating at 12V. It serves both high and low beam functions on the GMC 150 for 1956-1957, and also on 1958-1959 models equipped with a two-headlamp configuration, where a single unit handles both beam modes.
On 1958-1959 GMC 150 models equipped with four headlamps, the system splits beam duties between two distinct sealed beam types. The H5001, a 4-inch square unit, handles high beam, while the H5006, a 5.75-inch round unit, handles low beam.
The H5001 and H5006 are exclusive to the four-headlamp configuration found on 1958-1959 models. Neither type appears in any other year within these specifications, making them configuration-specific rather than general-fitment units.
The two-headlamp and four-headlamp configurations for 1958-1959 are not interchangeable in terms of bulb fitment. The H6024 used in the two-headlamp setup is a different physical format from both the H5001 and H5006 used in the four-headlamp setup, and the units cannot substitute for one another.
All sealed beam units listed across these specifications operate at 12V, which reflects the 12-volt electrical system that became standard in American vehicles during the mid-1950s, replacing the earlier 6-volt systems.
All bulb types in these specifications conform to ANSI standards recognized in the US and Canada. ANSI standardization for sealed beam headlamps defined fixed sizes and beam patterns, which allowed units from different manufacturers to be interchangeable within the same type designation.