1977 GMC Sprint

(GM photo)
Starting in 1975, the SP and El Camino SS packages could be ordered on any model. A 1975 or 1976 SS or SP would have four rectangular headlights if based upon the Classic model, or two round headlights if based upon the Standard model. Pictured is a Classic model 1977 GMC Sprint SP. Note the Corvette style rally wheels, which were part of the SP and SS packages from 1975 to 1977.