While they won't have the more robust flavor of the Calabrian chilis, crushed red pepper flakes can be substituted for the Calabrian chilis in a pinch. Consider using 1 ½ teaspoons of crushed red pepper, which is my preferred amount in the sauce of another spicy pasta, smoked sausage fra diavolo. Add them at the same time you would have added the Calabrian chilis so the flavor of the dried pepper flakes can heat and bloom before adding the bulk of the liquid ingredients.