California Classic Chrome Part Number CCC604 Steel , Triple Plated Copper/Nickel/Chrome For Small Block Chevy Engines 1970 - 1985 With LONG WATER PUMP Made From 0.50 Thick Steel Diameter Of 6 3/16 Inches Single Groove Pulley Long Water Pump Pulley 2 1/8 Inch Bolt Pattern Water Pump Pulley Has A Back Space Of 2 Inches.