I would pick a water pump based on impeller style instead of material. When I shopped around for a Pontiac pump, an iron one ended up having the factory style impeller fins. An aluminum one had the stamped steel impeller typical of a lot of aftermarket pumps.
A quick Google search showed the Flowkooler pump with a disc on the back of the impeller. That's probably meant to increase efficiency vs. an open impeller. (I'm not sure what the stock impeller looks like.)
A quick Google search showed the Flowkooler pump with a disc on the back of the impeller. That's probably meant to increase efficiency vs. an open impeller. (I'm not sure what the stock impeller looks like.)