I have a 79 Surfside
. I had a hinge pin that was not fully engaged into the lower part of the hinge. I took the hinge off to repair the pin. I think there is wood blocks inside the door and around the door frame that the hinges are screwed to. I replaced the existing rusted screws with new, slightly longer stainless steel screws and put a little butal tape around the screw before I screwed them back into the original holes. Be careful not to use too long a screw, right hole into the door. There is very little thickness to the door at that spot.
It seems these doors don't hang where you think they should, according to the body. The trailers that I've seen dont line up. The door line is about 3/8" lower then the body. Good luck and let me know if you get the door to line up.