Cook beef in large skillet over medium-high heat until brown, stirring to separate meat; drain fat. Reduce heat to medium-low. Add cream cheese, salt and chili powder; simmer 5 minutes.
Toss shells with butter; fill with beef mixture. Arrange shells in buttered 13 X 9-inch pan. Pour taco sauce over each shell. Cover with foil. Bake in preheated, 350 degree oven for 15 minutes. Uncover; top with cheese and chips. Bake 15 minutes more or until bubbly. Top with sour cream and onions. Garnish with lettuce, olives and tomatoes.