GMC C6000 Headlight Bulb Size

GMC C6000 headlight bulbs utilize H6054, H6024, and H4651 sizes for high beam applications, along with H6054, H6024, and H4656 sizes for low beam configurations. The replacement chart covers 1979 to 1990 model year data 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.

High Beam Headlight

Years	Bulb Size
1989-1990	H6054
1979-1988	H6054 (With 2 Rectangular Headlamps)
	H6024 (With 2 Round Headlamps)
	H4651 (With 4 Rectangular Headlamps)

Low Beam Headlight

Years	Bulb Size
1989-1990	H6054
1979-1988	H6054 (With 2 Rectangular Headlamps)
	H6024 (With 2 Round Headlamps)
	H4656 (With 4 Rectangular Headlamps)

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). 5x7-inch rectangular sealed beam unit. Not a replaceable bulb — the entire unit is replaced. 12V.	H6054
ANSI standard (US & Canada). 7-inch round sealed beam unit. Not a replaceable bulb — the entire unit is replaced. 12V.	H6024
ANSI standard (US & Canada). 4x6-inch rectangular sealed beam unit. Not a replaceable bulb — the entire unit is replaced. 12V.	H4651
ANSI standard (US & Canada). 4x6-inch rectangular sealed beam unit. Not a replaceable bulb — the entire unit is replaced. 12V.	H4656

Other Locations

Additional Notes

The GMC C6000 uses sealed beam headlight units across all specified model years, meaning the entire lens-reflector-filament assembly is replaced as one unit rather than replacing an individual bulb inside a housing.
All sealed beam types listed for the C6000 operate at 12V and conform to ANSI standards recognized in both the United States and Canada.
The H6054 is a 5x7-inch rectangular sealed beam unit. It serves as both the high beam and low beam on C6000 models equipped with 2 rectangular headlamps, covering the 1979-1990 model years for both functions.
The H6024 is a 7-inch round sealed beam unit used on C6000 models equipped with 2 round headlamps. It handles both high and low beam functions on those configurations for the 1979-1988 model years.
On GMC C6000 models equipped with 4 rectangular headlamps, the high beam and low beam positions use different sealed beam types. The H4651 fills the high beam position, while the H4656 fills the low beam position. Both are 4x6-inch rectangular sealed beam units, making them physically similar but not interchangeable between positions.
The 4-rectangular-headlamp configuration is the only setup in these specifications where the high beam and low beam require distinct part numbers, making correct position identification critical during replacement.
For the 1989-1990 model years, the specifications list only the H6054, indicating those years were available solely with the 2 rectangular headlamp configuration according to the provided data.
Because the H4651 and H4656 share the same 4x6-inch rectangular form factor, substituting one for the other would place an incorrect beam pattern in a given headlamp position, which affects both illumination performance and compliance with lighting standards.