Open the door and lift on the bottom edge. If it has quite a bit of play,you need new pins and bushings in the hinges. If there isn't excessive play,swing the door almost shut. Do the body lines match up pretty well? If they do,loosen the striker bolt,and adjust it up or down,to match the centerline of the latchjaws when open,and then tighten it back up. should shut perfectly. If the body lines don't match up,check for damage or rust at the cab mount,rocker panel area. If that's ok,it's time for the old 2x4 trick. Place a short piece of 2x4 about 1ft in the front doorjamb by the lower hinge, close door until it contacts the wood,now apply pressure to the out side of the door,you will feel the back edge lifting up. Be careful,too far is very bad so go easy on it. Hank