68 Barracuda 440 getting hot in traffic

Check your ignition timing. Maybe a couple more degrees of timing at idle will help keep it cool. What do your plugs look like? Do you have a wide band? A lot of cooling problems are actually engine tuning problems. Have you had the radiator rodded out? Even if it looks nice it could've just been a spray can resto. If you want a solve a problem you have to stop making assumptions and go verify everything yourself.