The Ferrari 328 GTS front and rear side marker bulbs both utilize a 158 size bulb specification. The replacement chart covers vehicle production spanning 1986 to 1989.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Ferrari 328 GTS uses the 158 bulb across all four model years (1986-1989) for both front and rear side marker positions.
The 158 is an ANSI-standardized bulb type, meaning its physical and electrical specifications conform to a defined North American standard recognized in both the United States and Canada.
The 158 bulb belongs to the T10 wedge family, a miniature form factor that uses a wedge-shaped base rather than a metal contact pin, relying on tension from the socket to maintain an electrical connection.
The 158 operates at 12 volts and draws 3 watts, placing it among the lower-wattage bulbs in automotive applications, consistent with its use in side marker rather than primary lighting functions.
Because the 158 designation is ANSI-standardized, bulbs carrying that designation from different manufacturers share the same base type, voltage rating, and wattage, making cross-brand substitution possible within that standard.
The T10 wedge base format used by the 158 is a common platform that also underpins several other ANSI bulb numbers, though those variants may differ in wattage or filament configuration and are not necessarily interchangeable with the 158.
The front and rear side marker positions on the Ferrari 328 GTS share an identical bulb specification, meaning the same 158 bulb serves all four side marker sockets on the vehicle.