GMC P25 and P2500 models utilize H5001 bulb size for high beam headlights and H5006 bulb size for low beam headlights. The replacement chart covers vehicle production years from 1967 to 1972 with corresponding bulb specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The GMC P25 / P2500 uses the H5001 for high beam headlights and the H5006 for low beam headlights across the full 1967-1972 model range.
Both the H5001 and H5006 are sealed beam units, meaning the lens, reflector, and filament are fused into a single housing. When a filament fails, the entire unit requires replacement rather than an internal bulb swap.
The H5001 is a 4-inch square sealed beam unit operating at 12 volts and conforms 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 12 volts and built to the same ANSI standard applicable in the United States and Canada.
The square form factor of the H5001 and the round form factor of the H5006 are physically incompatible with each other, making the two units non-interchangeable between the high beam and low beam positions on the GMC P25 / P2500.