Passenger door stiff/hard to close

[Judgeyoung]

My old '72 GMC is in good original shape. The original door hinges seem to have very little slack. I put new door seals on and they seal great, but even before the weatherstrip replacement, the passenger door has always been very stiff to close. It will stop anywhere in the travel if not pushed and is very stiff to push, requiring a real pull/shove to close well.

I lubed the hinges and the little slider stop piece, but it made no discernible difference, but something is binding.

The driver door is smooth and easy. What am I missing?