Tacos in pasta shells

Pasta and macaroni Mexican cuisine

1¼ pounds lean ground beef 1 (3 ounce) package cream cheese 1 teaspoon salt 1 teaspoon chili powder 18 jumbo pasta shells 2 tablespoons butter, melted 1 cup taco sauce 1 cup shredded Cheddar cheese 1 cup shredded Monterey Jack cheese 1½ cups crushed tortilla chips 1 cup sour cream