There was a discussion on the C Body Dry Dock board not long ago about aftermarket aluminum water pumps for big blocks. Seems the stuff out there does not do as good a job of cooling as the OEM cast iron pump does. I started a similar thread on that forum. So far, I found out that Mopar Performance makes an aluminum pump that is a similar design to the cast iron one. Looks like that might be the best bet...Thought I'd ask you guys as well...

I've got a 67 300 'vert with the 440 High Po engine and it does not have A/C. She kinda runs hot in the summer when stuck at traffic lights, so if I decide to replace the pump with an aluminum one, it has to perform as well or BETTER than the OEM big block pump.