Do you mean you can still find what we used to call “factory pack” paint ? If so that would be the way to get the best chance for a match of the flake and color. It looks to me that the repaint did not match very well comparing the door to the quarter panel. Matching the panels is going to be tough without blending into the door. Even when those cars were new and with factory packaged paint you could see the repaint comparing panel to panel. Mopars with their acrylic enamel were not the best finishes in their day. Especially the metallics.