Preheat oven to 350. Lightly oil a 13 X 9 inch shallow casserole dish.
Bring a large pot of water to boil. Add jumbo shells a few at a time, stirring after each addition, so the shells stay separate while cooking. Return to a boil and cook, uncovered, 8 to 10 minutes or until just firm-tender. Do not overcook. Drain and cool in a single layer on a sheet of waxed paper to prevent shells from sticking together.
Wash spinach well in lukewarm water to remove grit. Cook in a medium nonstick skillet in just the water that clings to the leaves, tossing just until wilted. Wrap in a paper towel and press out the moisture. Finely chop cooked spinach.
Beat the eggs in a large bowl. Add spinach and stir until combined. Add mozzarella, 1/2 cup of the parmesan, parsley, salt and pepper and stir until all ingredients are well combined. Fill each jumbo shell with 1 1/2 Tbs of the spinach mixture.
Pour 1 cup of the pasta sauce in the bottom of prepared casserole dish. Arrange the shells in one layer. Spoon over the remaining sauce. Cover loosely with foil. Bake 30 minutes. Remove foil and sprinkle with remaining 1/4 cup of parmesan cheese. Bake, uncovered, 5 minutes, or until cheese is melted.