The GMC P35 / P3500 uses an H5001 bulb size for high beam headlights and an H5006 bulb size for low beam headlights. The replacement chart covers vehicle production years from 1967 to 1972 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 GMC P35 / P3500 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 the 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 as the H5001. Its round form factor distinguishes it physically from the square H5001 used in the high beam position.
Because the H5001 and H5006 differ in both shape and size, the two units are not interchangeable with each other. The square profile of the H5001 and the round profile of the H5006 correspond to separate mounting positions on the GMC P35 / P3500.
The consistent use of H5001 and H5006 across all six model years indicates that no fitment changes were introduced to either headlight position during the 1967-1972 production span.