The Buick Gran Sport uses an H5001 bulb size for high beam headlights and an H5006 bulb size for low beam headlights. The replacement chart covers 1965 through 1967 model 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 Buick Gran Sport uses the H5001 sealed beam unit for high beam headlights across the 1965-1967 model years.
Low beam headlights on the 1965-1967 Gran Sport use the H5006 sealed beam unit.
The H5001 is a 4-inch square sealed beam unit operating at 12V and conforming to ANSI standards recognized in both the United States and Canada.
The H5006 is a 5.75-inch round sealed beam unit, also rated at 12V and built to the same ANSI standard applicable in the United States and Canada.
Both the H5001 and H5006 are sealed beam units, meaning the lens, reflector, and filament form a single non-serviceable assembly. When a filament fails, the entire unit requires replacement rather than an internal bulb swap.
The square profile of the H5001 and the round profile of the H5006 make the two units physically incompatible with each other's housings, and one cannot substitute for the other in the Gran Sport's headlight system.