1979 GMC C1500 Engine: 5.7L V8; Standard Rotation; Optional Non-Thermal Fan Clutch; w/ Standard Duty Fan Clutch;. 1979 GMC C1500 Engine: 5.0L V8; Standard Rotation; Optional Non-Thermal Fan Clutch;. 1980 GMC C1500 Engine: 5.7L V8; Standard Rotation; Optional Non-Thermal Fan Clutch; w/ Standard Duty Fan Clutch;.