When doing replacement or upgrading on 1978 – 1987 GMC Caballero, the bulb size guide is necessary for you to take the reference.
Jump to corresponding car model with the catalog bellow.

Low Beam Headlight 1982 – 1987 H4656
High Beam Headlight 1982 – 1987 H4651
High Beam and Low Beam Headlight 1978 – 1981 H6054
Back Up Light 1978 – 1987 1156
Brake 1978 – 1982 1157
1983 – 1987 2057
Dome Light 1978 – 1979 561
Front Side Marker 1978 – 1987 194
Front Turn Signal 1978 – 1982 1157
1983 – 1987 2057
License Plate 1978 – 1987 194
Parking Light 1978 – 1979 1157
1980 – 1982 194
1983 – 1987 2057NA
Rear Side Marker 1978 – 1979 194
Rear Turn Signal 1978 – 1982 1157
1983 – 1987 2057
Tail Light 1978 – 1982 1157
1983 – 1987 2057
Courtesy 1980 – 1987 561
1978 – 1979 631
Engine Compartment Light 1978 – 1979 1003
1980 – 1987 1156
Glove Box 1978 – 1987 1895
Radio Display 1982 – 1987 194
1980 – 1981 73