I don't think the impeller is critical which way it's made? It's going to do the same thing either way it's turned. I like your original pump better than the one with a cheaper stamped impeller.
I bet some of your heat is coming from being lean in the cruise or power mode. Today's gas needs to be jetted much richer than straight gas and that surely will add heat to your new motor being lean. Also you sure you have enough timing, that will cause it to run hot also.
