1967 GMC C25/C2500 Suburban Engine: 4.1L L6; Standard Rotation; Optional Non-Thermal Fan Clutch;. 1967 GMC C25/C2500 Suburban Engine: 4.6L V8; Standard Rotation; Optional Non-Thermal Fan Clutch;. 1967 GMC C25/C2500 Suburban Engine: 4.8L L6; Standard Rotation; Optional Non-Thermal Fan Clutch;.