I do t know about where you are, but the rain was heavy sideways from the SW overnight into this morning. Maybe that helps figure out which direction the rain hit the car and how it might have gotten in.
You might also want to get one of those inexpensive car covers I had on the ‘66 Dart to keep the weather out.
It was some pretty crazy rain. No doubt thats why so much got in. Passenger side is dry. Im thinking door seal since a little was in the back floor too. yep, thinking its time for a cover. Where did you get that one?