GMC C6000 Headlight Bulb Size

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.