GMC 250 front and rear side marker bulbs utilize a 63 size across both positions. The replacement chart covers 1951 to 1955 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 GMC 250 uses the 63 bulb for both front and rear side marker positions across the 1951-1955 model years.
The 63 bulb follows the ANSI standard, which governs bulb specifications in the United States and Canada.
This bulb operates on a 12-volt electrical system, consistent with the standard automotive voltage adopted broadly in the mid-20th century.
At 0.63 watts, the 63 bulb draws very little power, reflecting its role as a low-intensity marker light rather than a primary illumination source.
The 63 bulb uses a BA9s base, a miniature bayonet-style fitting with a 9mm collar width, commonly found in small indicator and marker applications.
As a single-filament bulb, the 63 serves only one lighting function per socket, with no secondary filament for a dual-intensity mode.
The front and rear side marker positions on the GMC 250 share the same bulb type, meaning a single part number covers all four marker sockets on the vehicle.