Dart swinger drip rail weatherstripping

I'd be tempted to take the weatherstripping off the Dart the door came from and put it in there to see what happens. Looks like you have it lined up pretty good. You may be able to adjust the weatherstripping channel inwards a little bit so it will line up. Also look at the weatherstripping channel on the donor car to see if there's a difference between it and what's on the 75. It might be different due to vent window and slick window....oops, winder! :)