Door hard to close - any ideas?

[tucsonjwt]

I just replaced the bushings and pins in the driver's door of my 83 C20. I previously replaced the rubber door seal and the striker bolt. The door has a nice even reveal all around the opening, the mid door line is even with the corresponding line on the box, the hinges were reinstalled in exactly the original position. The door is now snug with no drop/play vertically, but it still requires a good hard slam to get it to close completely.

The flaps behind the vent in the bottom of the door are clear, so I don't think it is a cabin pressure issue. However, when I leave the passenger door open the driver's door is easier to close - probably not perfect but much better than with the passenger door closed.
Does anyone else have this issue or have any ideas on how to fix it?