To be a bit more helpful: I assume you want to actually have a usable stock, not a welded-shut "Tacti-Cool" foolish piece of nonsense.
So:
You can convert it to a SBR (Short barrel Rifle) by filling in a BATFE Form 1, and sending it with a $200 check to the BATFE and then waiting about a year for approval. You'll then need to obtain permission from the BATFE every time you want to take it to a different state. It becomes a NFA firearm (National Firearms Act), no different than a machine gun. In order to have your Form-1 approved, you will need to have your local Chief of Police sign it before you submit it, or you will need to form a Corporation or Trust to own it. Is that all worth it? If so, that's what you do. Many of us have done this with other pistols, converting them to short barreled rifles, and enjoy the results.
With that said, I must add this: The Enforcer is not terribly well regarded by anyone. Universal, the manufacturer, did not use the original M-1 carbine design or parts to manufacture their Carbines and they are considered to be the worst M-1 carbines built. The Enforcer is the least useful of the M-1 versions. Very few people would invest the time and effort to register one as a SBR when there are other choices with far more utility and reliability.
Willie
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