Preheat oven to 375°F and grease a 9x13-inch baking dish.
Cook jumbo pasta shells according to package directions until just slightly underdone, then drain and set aside to cool.
In a medium bowl, mix together the chili, 1 cup of shredded cheddar cheese, sour cream, and chili powder until well combined.
Carefully stuff each pasta shell with the chili mixture and arrange them in the prepared baking dish.
Top the stuffed shells with remaining 1/2 cup cheese and salsa.
Bake for 20-25 minutes until cheese is melted and bubbly.
Garnish with diced green onions before serving.