For a street car the faster you can spin the water pump the better. If you start driving at high speeds then you'll have to rethink the drive ratio. The factory engineers changed the ratio for the engines that were capable of higher speeds since they were most likely worried about cavitation. For a street car I'd duplicate the HD cooling package that you could get with the tow package. I think police cars and taxi cabs also got the HD cooling package. It should be spelled out in the master parts book for your make and model.