Description: Water Pump Impeller (service replacement)
Year: 1967-70 
Model: Mustang, Shelby, Cougar
Finish:: Bare steel
Dimensions: 5/8" bore, 4.9062 OD, 0.4219" center hub height

Jack's Comments:

This stamped steel 390, 428 PI, 428 S/CJ water pump impeller that is the only available replacement available.  We have used this impeller for our rebuild water pump service for several years and have found it to cool effectively as the production original cast iron impellers.  We know this basic design may reduce power a little above 5000 RPM's but unless you have a good original cast iron impeller this is the only option.