Radiator Bracket.

Since the date on your door plate is just a scheduled date, you can't say for sure when the car was actually built. Although, if you're trying to get the car numbers correct and using the door plate for a reference, then a 3rd week of June radiator date would not fit well. Of course, your goals with the car may or may not dictate that something like this be absolutely correct.

Keep in mind there are different radiator types depending on the assembly plant. San Jose had numbers stamped into the top tank, Dearborn/Metuchen had stamped numbers on the side support. Top tanks for both were different shape.