Water pump impeller styles?

Johnny Dart said

That's a pretty trick pump. That's cool they are selling them now with the non cavitation plate. Flowkooler was the only company I know of selling a pump with the plate.

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Edelbrock's is one of the slickest impeller of that variety.
Unfortunately I found it was neccessary to do a little clearence grinding on the outside of the inlet. You can see the point of contact in the photo. I wrote them about it - not sure if they followed up with a change. (This was in 2005)