Back in the day when Bubba was a youngin that was an acceptable thing to do to just about any sulplus rifle. Of course today it's "How could you do such a thing". It does appear to have been nicely done. Of course you may be able to find a correct stock for it and return it to greatness once again.
But then again the barrel is a replacement as IBM made their own barrels and did not use any Underwood barrels.