Bring a large pot of water to a boil. Add potatoes, and cook for about 10 minutes, or until tender. Drain, and set aside to cool.
Meanwhile, in a large bowl, stir together the salad dressing, mayonnaise, green onions, dill, mustard, lemon juice, and pepper. When the potatoes are cooled, stir into the bowl until coated. Refrigerate for a couple of hours to blend flavors before serving.
