GMC Truck front and rear side marker bulbs utilize a 63 size across both positions. The replacement chart covers 1950 to 1955 production years 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 Truck uses the type 63 bulb for both front and rear side marker positions across the 1950-1955 model years.
The type 63 is an ANSI-standardized bulb recognized in both the United States and Canada, meaning it conforms to a shared North American specification rather than a regional or proprietary standard.
The type 63 operates on a 12-volt electrical system, consistent with the standard automotive voltage used in these vehicles.
At 0.63 watts, the type 63 draws very little power, which reflects its role as a low-intensity marker lamp rather than a primary lighting source.
The type 63 is a single-filament bulb, meaning it produces only one level of illumination with no secondary brightness mode such as a dim or bright function.
The BA9s base is a miniature bayonet-style fitting with a 9mm collar, commonly found in small indicator and marker lamp sockets.
The identical bulb type across both the front and rear side marker positions means a single bulb specification covers all side marker sockets on the GMC Truck for the 1950-1955 model years.