'66 A Body folks, please...

What temp is it running? I can almost guarantee that a hood to core support seal won't help in this situation.

At speed, a butt load of air is crashing into the condenser and radiator, more than enough to cool your engine.

The idea that hot, under-hood air is getting kicked back around or too much is going over or missing the radiator isn't realistic.

I would make sure the condenser is clean and the fins are n good shape. Same with the radiator, loosen the condenser and take a look. You can use a fin comb or similar tool to straighten damaged fins.

My guess is that it's a capacity issue. You just need more radiator.

Or.... You don't have an issue at all. Many people on here rely on a factory gauge that doesn't tell the actual temperature.

People panic when they see 200 or 205 on hot days. That's not hot.