1988 Chevrolet R20 Engine: 4.3L V6; Reverse Rotation; Optional Standard Duty Thermal Fan Clutch; Fan Mounting Holes are 10 mm.;. 1988 Chevrolet R20 Engine: 5.0L V8; Reverse Rotation; Optional Standard Duty Thermal Fan Clutch; Fan Mounting Holes are 10 mm.;.