Combine flour, sugar, and salt in a large bowl.
Cut in ¾ butter thoroughly with a pastry blender until mixture resembles very fine crumbs.
Press mixture evenly into 13"x9" 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 ½ 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 34-35 minutes or until set.
Cool completely in pan on a wire rack. Cut into bars.
