There is no such thing as CW and CCW Pontiac water pumps. Yes, the impeller looks different in some designs. And yes, the stamped impeller looks different (some folks say backwards) than the cast impeller. But they are all built to turn the same direction and provide coolant flow in the same direction.
Instead of continuing my rant, I'll point you to my previous rant on this subject:
http://forums.maxperformanceinc.com/...d.php?t=593938
which also includes part numbers from NAPA if you follow the thread far enough.