Combine flour, sugar, and salt in large bowl; cut in 3/4 cup butter thoroughly with a pastry blender until mixture resembles very fine crumbs. Press mixture evenly into a greased 13" x 9" pan, using a piece of plastic wrap to press crumb mixture firmly in pan. Bake at 350° for 17 to 20 minutes or until lightly browned.
Combine brown sugar, corn syrup, and 1/2 cup butter in a saucepan; bring to a boil over medium heat, stirring gently. Remove from heat. Stir one-fourth of hot mixture into beaten eggs; add to remaining hot mixture. Stir in pecans and vanilla. Pour filling over crust. Bake at 350° for 34 to 35 minutes or until set. Cool completely in pan on a wire rack. Cut into bars.