In a large bowl, combine brown sugar, cinnamon and salt. Add pumpkin, eggs, corn syrup and vanilla; beat well. Pour into the pastry shell. Sprinkle with chopped pecans. Place pecan halves around the outer edge of filling. Bake at 425° for 15 minutes. Reduce the heat to 350°; bake 25 more minutes or until a knife inserted in the center comes out clean. Cool. Serve with whipped cream if desired.