[Keith Seymore]

These doors never closed well, because there is not a lot of "mass" to them to help generate momentum, and because they are pushing a lot of air into a small cavity (the regular cab volume) and it can't vent quickly enough.

If rolling the window down slightly helps significantly then I predict it is an "air" problem rather than a mechanical or adjustment issue with the hinges/pins/latches. You can remove the PRVs ("pressure relief valves") in the bottom of the doors and that may help, but you may notice a bit more road noise and dust intrusion.

For over forty years now (our first squarebody was a '75) I just always planned on pushing the door home, rather than swinging it and expecting it to latch.

K