1979 GMC G2500 Engine: 4.1L L6; Standard Rotation; Non-Thermal Fan Clutch; w/o A/C;. 1980 GMC G2500 Engine: 4.1L L6; Standard Rotation; Non-Thermal Fan Clutch; w/o A/C;. 1981 GMC G2500 Engine: 4.1L L6; Standard Rotation; Optional Non-Thermal Fan Clutch; w/o A/C;.
