I recently restored a nice '71 442. It is an a/c car. I had the radiator rodded and put on a new water pump, thermostat, etc. I wanted to make sure that it ran cool enough on hot southern summer days. It seems to do fine. Those cars, back in the day, had some rubber seals that went down in the radiator support. When you pushed the radiator down in the support these seals keep air from flowing around the radiator. There are other seals on the corner of the radiator, on the top and also on the bottom. All are meant to keep air flowing across the radiator. I failed to put the seals down in the radiator support. Do you folks think that would have much affect? Are they considered essential, especially when running a stock a/c on a hot day? (The engine is stock.) I am going on the Hot Rod Power Tour in June and I need no cooling issues. Thanks.

 

If you have any concerns install a external cooling fan & if you are using R 134@ it runs at a higher head pressure

 

The rubber flaps are easy to install anytime. There are two on the top and one big one at the bottom of the bumper. This is more important to ram large amounts of air through the radiator at cruise.
The side seals are good to have, but leaving them out will not cause overheating (the gaps are too small).
Make sure your shroud is there and the fan clutch works (roaring noise upon cold startup, which lasts a few minutes, and when idling hot).
Replace radiator cap if it is old.

If is runs okay now, you should be fine.