A couple other ideas. Look at the underside of the door, make sure the openings there aren’t clogged with rust/debris. Use a screwdriver or something to probe, make sure they are all open. Water will always get into the door b/c the seal to the window is never 100% water tight, since the window has to go up and down. The door is designed so water that gets in drains right back out the bottom of the door, and too the outside by the way the door threshold is shaped. But that only works if the holes in the bottom of the door are open.
Also, do you see those vents just under the windshield? On the outside of the car? They allow fresh air into to the HVAC system, but rain will get in there too. On my early 70’s Ford truck there’s a sort of plastic bucket gadget near where your feet go designed to separate the water (which is heavier so it accumulates at the bottom of the bucket) from the fresh air. The drain hole in the bottom of that bucket can get clogged. I had to clean these holes out on both the passenger side and the driver side just prior to this big rainstorm we have had in Calif in fact, b/c water was getting in and accumulating on my poor truck’s floor pan. I noticed today cleaning those drains fixed the problem, as no more water on the floor, even after 3 inches of rain in 24 hours. Not sure if this technique is used with cars of your vintage, but there has to be some way to drain water that gets into those vents back out of the car, and the path could be clogged.
It’s a good idea to occasionally use a shop vac to vacuum leaves and other debris from those fresh air vents under the windshield, can help prevent the drain holes lower down in the system from clogging. I do this every 3 months.