Place caramels and evaporated milk in a heavy saucepan. Heat over medium-low heat, stirring continually, until smooth, about 5 minutes. Stir in ½ cup chopped pecans. Pour into piecrust. Combine cream cheese, sour cream and milk in a blender. Process until smooth. Add pudding mix; process for about 30 seconds longer. Pour pudding mixture over caramel layer, covering evenly. Chill, loosely covered, until set, about 15 minutes. Drizzle fudge topping over pudding layer in a decorative pattern. Sprinkle top of cake with remaining pecans. Chill, loosely covered, until serving time.