This is for the small block Chevy engine with short water pump.
CHEVY SMALL BLOCK CHROME ALUMINUM CRANK PULLEY - 3 GROOVE (LWP)
For CHEVY SMALL BLOCK CHROME STEEL CRANKSHAFT PULLEY - SHORT (1 GROOVE)
For CHEVY SMALL BLOCK CHROME STEEL CRANKSHAFT PULLEY - LONG (1 GROOVE)
Fit Chevy Small Block Chrome Aluminum Crank Pulley 3 Groove Short SWP
Fits 1955-68 Chevy Small Block Chrome Steel Crankshaft Pulley Short (1 Groove)