1977 GMC K35 Engine: 4.8L L6; Standard Rotation; Standard Duty Thermal Fan Clutch;. 1977 GMC K35 Engine: 5.7L V8; Standard Rotation; Optional Standard Duty Thermal Fan Clutch;. 1978 GMC K35 Engine: 5.7L V8; Standard Rotation; Optional Standard Duty Thermal Fan Clutch;.
