To prepare crust, combine crumbs, margarine, and three tablespoons sugar in a mixing bowl. Press mixture firmly in a 9" pie pan. Chill one hour, or until firm. Or, bake in a 375 oven for ten minutes or until edges are brown. Cool on rack before filling. Preheat oven to 325. Place crust on baking sheet; set aside. In a mixing bowl, combine cream cheese, remaining sugar, lemon juice, vanilla extract, salt, and eggs. Mix until smooth. Pour mixture into crust. Bake for 25 minutes or until inserted knife comes out clean. Spread filling evenly on top of cooled cheesecake. Sprinkle toasted walnuts on top.