When doing replacement or upgrading on 1971 – 1977 GMC Sprint, the bulb size guide is necessary for you to take the reference.
Jump to corresponding car model with the catalog bellow.

Low Beam Headlight 1976 – 1977 H4656
High Beam Headlight 1976 – 1977 H4651
High Beam and Low Beam Headlight 1971 – 1975 H6024
Back Up Light 1971 – 1977 1156
Brake 1971 – 1977 1157
Dome Light 1974 – 1977 561
1971 – 1973 578
Front Side Marker 1971 – 1977 194
Front Turn Signal 1971 – 1977 1157
License Plate 1974 – 1977 168
1971 – 1973 97
Parking Light 1971 – 1977 1157
Rear Side Marker 1971 – 1977 194
Rear Turn Signal 1971 – 1977 1157
Tail Light 1971 – 1977 1157
Courtesy 1971 – 1973 212-2
1974 – 1977 89
Engine Compartment Light 1971 – 1977 1003
Glove Box 1974 – 1977 1893
1971 – 1973 1895
Map Light 1974 – 1977 561
Radio Display 1971 – 1973 1816
1974 – 1977 37