Preheat the oven to 375°F.
Cook the jumbo pasta shells according to package instructions until al dente. Drain and set aside.
In a large mixing bowl, combine ricotta cheese, 1/2 cup mozzarella cheese, Parmesan cheese, sun-dried tomatoes, basil, garlic powder, onion powder, salt, and black pepper. Mix until well combined.
Spread 1 cup of marinara sauce evenly on the bottom of a 9x13-inch baking dish.
Stuff each cooked pasta shell with the ricotta mixture and place them in the baking dish, open side up.
Pour the remaining marinara sauce over the stuffed shells. Sprinkle the remaining mozzarella cheese on top.
Drizzle olive oil over the dish.
Cover the baking dish with aluminum foil and bake for 25 minutes. Remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and golden.
Let cool for 5 minutes before serving.