Old Master is right, replace the door pins and bushings. And also lubricate them and all other hinges such as the hood and hatchback with a light oil every time you do an oil change. My 1950 GMC truck manual mentions that service stations often overlook lubricating body parts, but they are part of the scheduled maintance.
If you do it yourself have some help ready, those doors are heavy. Link to DIY is here:
http://www.automotiveforums.com/vbul...d.php?t=363334
As far as adjusting the gap when closed, look at the the striker post. It should have a star type torques reciever in it that will allow some adjustment but replace the worn parts first.