crank Shaft Pulley Spacer1979 & Earlier 351W4-Bolt Pattern0350 Thick These crankshaft spacers are specifically designed for use with Ford Racings crank dampers to achieve proper belt alignment on earlier model 50L and 58L engines They are precision-machined on cNc equipment for a perfect fit, have a 3 or 4-bolt pulley pattern, and are available in three thicknesses for different enginesUsed For Proper Pulley AlignmentDrilled For 3 And 4 Bolt DamperMade in the USA