I have a J STEVENS ARMS .410 single shot shotgun. on the bottom of the barrel it is stamped 332 and inside the receiver stamped 332C. Can anyone
tell me the model of this and where I can purchase a firing pin?
Marks like you describe are usually internal production control marks on Savage/Stevens/ Springfield shotguns.
There should be a small model number somewhere on the upper half of the barrel near the breech, or the side of the frame.
GunParts Corp (aka Numrich) has a website. They likely will have a firing pin ; but it will likely require significant time consuming fitting based on my experiences. If not properly fitted the shotgun will be dangerous or not work.