GMC P35 / P3500 front and rear turn signal bulb sizes include 1156, 1073, 1034, and 199 options. The replacement chart covers 1967 through 1972 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 1156 bulb is the most frequently specified type across the GMC P35 / P3500 turn signal positions, appearing in both front and rear applications for the 1970-1972 model years.
The 1156 is a single-filament bulb rated at 12V and 21W, fitted with a BA15s bayonet base, and recognized under ANSI standards in both the United States and Canada.
The 199 bulb, used in the rear turn signal position on the GMC P35 / P3500 for 1969 and 1972, is a variant of the 1156 and shares the same 12V, 21W rating with a BA15s bayonet base.
Despite the 199 and 1156 sharing identical electrical ratings and base type, they carry distinct ANSI designations, which may affect fitment depending on the socket and housing design of the specific model year.
The 1073 bulb, used in both front and rear positions for 1968, is a lower-wattage variant of the 1156, rated at 12V and 13W, and also uses a BA15s bayonet base.
The reduced wattage of the 1073 relative to the 1156 means the two bulbs are not electrically interchangeable without consideration of the vehicle's turn signal flasher unit, which is typically calibrated to a specific load.
The 1034 bulb, specified for both front and rear turn signal positions on the 1967 model year, is a dual-filament type rated at 12V with a 21/5W output, fitted with a BAY15d bayonet base.
The BAY15d base of the 1034 is physically distinct from the BA15s base shared by the 1156, 1073, and 199 bulbs, making the 1034 incompatible with sockets designed for those single-filament types.
The 1034 is noted as a variant of the 1157, a widely used dual-filament automotive bulb, with the two filaments typically serving separate functions such as turn signaling and running light operation within a shared housing.
Front and rear turn signal positions on the P35 / P3500 do not consistently share the same bulb type across all model years, as seen in 1969 and 1972 where the front uses a 1156 while the rear uses a 199.