Plymouth GTX high beam headlight bulbs use H5001 size while low beam headlight bulbs use H5006 size. The replacement chart covers 1967 to 1971 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 Plymouth GTX used the H5001 sealed beam unit for high beam headlights across all model years from 1967-1971.
The H5001 is a 4-inch square sealed beam unit operating at 12V, conforming to ANSI standards recognized in both the United States and Canada. As a sealed beam design, the entire unit is replaced rather than an internal filament or capsule.
Low beam headlights on the GTX followed the same 1967-1971 fitment pattern, specifying the H5006 sealed beam unit throughout.
The H5006 is a 5.75-inch round sealed beam unit, also rated at 12V and built to the same ANSI standard as the H5001. Like the H5001, it is replaced as a complete assembly.
The H5001 and H5006 are not interchangeable with each other. The high beam position requires the 4-inch square H5001, while the low beam position requires the 5.75-inch round H5006. Swapping these units between positions is not possible due to their differing form factors.
Both sealed beam types predate the widespread adoption of halogen and composite headlight assemblies, meaning replacement units must match the sealed beam format rather than a separate bulb-and-housing configuration.