Preheat over to 350 degrees. Wash the rice thoroughly under cold running water and drain. Reserve. Wash both the mussels and clams thoroughly until all sand has been removed. Do not soak them in cold water. Dry the fish pieces thoroughly with paper towels and season with salt and pepper. In a large skillet, heat 1/4 c olive oil. When it is very hot add the fish cubes and brown them on all sides. Remove them to a side dish and reserve. To the fat remaining in the skillet add the shrimp and cook them over medium heat until they turn bright pink. Season with salt and white pepper. Remove the cooked shrimp to a side dish and reserve. Add 2 T olive oil to the skillet. Add the onion, garlic and red pepper slices and cook until the onions are very soft and lightly browned. Be sure not to burn the mixture. Add the tomatoes and proscuitto, chilies and saffron. Season the mixture with salt and pepper, oregano and basil. Bring to a boil and cook, stirring constantly, scraping the bottom of the pan well, until most of the tomato juice has evaporated. Add the rice and 3 1/2 cups of chicken stock. Bring the mixture to a boil again and cook over medium heat until 1/2 of the broth is absorbed. Pour half the rice mixture into an earthenware casserole. Make a layer of fish cubes and Chorizo and top with the remaining rice. Cover the casserole and bake the rice for 25 minutes. Uncover the casserole and fold the shrimp and peas lightly into the rice. Cover again and continue baking for 10 to 15 minutes or until the rice is tender and all the broth has been absorbed. If the rice seems dry, yet still too crisp, add the remaining chicken stock. Uncover the casserole and bury the clams and mussels in the rice. Cover the casserole again and cook for another 10 to 15 minutes or until the shells of both mussels and clams have opened. Discard any mussels or clams that have not opened. Garnish the paella with pimiento strips and lemon quarters. Serve directly from the casserole.