The 1977 model was changed around march to have different design features. Based on when your car was manufactured will determine if you have an early or late C3. Some identifiers of the split will be: Alarm switch in the fender is early / Alarm switch in door lock is late, T-Top weatherstrip has 18 pins late / T-Top weatherstrip has 19 pins early, Most early 1977's have a Orange painted engine / Most late 1977's have a Blue painted engine.