1965 Dart window/door gaskets

I think you mean "window felts". I bought a set for my 1965 Dart 2-door, probably ebay. Still haven't finished painting so I can install them. Yes, it is "by design" that water runs inside the door and drains out the bottom. 1990's cars started using ones more like wiper blades that limit the water, but the door internals are still designed to tolerate water. That is why there is a "water shield" between the door and inner trim panel. Some sets don't come with clips and expect you to somehow transfer your old rusty clips onto the new ones.