What? An edelbrock with a casting problem? I thought it was only Dove that had casting problems! (All the forgoing is slight sarcasm.) With any FE waterpump, it might make sense to check the impeller. To start with, edelbrock used stamped steel impellers and those early ones often had overheating problems for some reason. A cast aluminum impeller and back plate and a good gasket and you should be good to go.
KS