Stuffed Quahogs

Name: Stuffed Quahogs
Ingredients: 10 lb. quahog or topneck clams, scrubbed; 8 oz. stale soft white sandwich bread, torn into 1 pieces (about 7 cups); 1 green bell pepper, ribs and seeds removed, coarsely chopped; 1 red bell pepper, ribs and seeds removed, coarsely chopped; 1 small onion, coarsely chopped; 6 Tbsp. unsalted butter, divided; ¾ tsp. kosher salt, plus more; 1 tsp. crushed red pepper flakes; Paprika and lemon wedges (for serving)