Ford Custom front side marker bulbs utilize 194, 161, or 1034NA sizes, while rear side marker bulbs use 194 or 161 sizes. Replacement chart data covers 1968 through 1972 production years.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 194 bulb is the most frequently specified size across the Ford Custom side marker data, appearing in both front and rear positions for the 1970 and 1972 model years.
The 194 is a T10 miniature wedge bulb rated at 12V and 3.78W, conforming to ANSI standards for the US and Canadian markets.
The 161 bulb shares the same T10 miniature wedge form factor as the 194 but operates at a significantly lower wattage of 1W, making the two electrically distinct despite their physical similarities.
The T10 wedge base used by both the 194 and 161 bulbs allows them to fit the same socket type, though their differing wattage ratings means they are not functionally interchangeable without consideration of circuit requirements.
The 1034NA is specified for the Ford Custom front side marker on the 1968 model year and differs substantially from the other bulbs in the data, using a BAY15d bayonet base rather than a wedge base.
The BAY15d base of the 1034NA is a dual-contact bayonet fitting, which is physically incompatible with the T10 wedge sockets used by the 194 and 161 bulbs.
The 1034NA is a dual-filament bulb rated at 21/5W, meaning it supports two separate brightness levels, a characteristic not present in the single-filament 194 or 161 bulbs.
The 1034NA features natural amber glass, which produces its color through the lens material itself rather than through a clear bulb behind a colored housing.
The 1034NA is classified as a variant of the 1157 bulb, indicating it shares the same base and general electrical configuration while differing in its amber glass construction.
All three bulb types in the Ford Custom side marker specifications conform to ANSI standards and are rated for 12V electrical systems, consistent with standard automotive voltage.