Deer Creek,
If there is ample stock, your barrel thickness in the last several inches from the muzzle, I don't see why you couldn't have one or even both of your barrels bored and threaded to accept choke tubes, rifled or other. If wanted, carefully fitting (holding close tolerances) with the correct precautions to ensure that it or they are in for good along with the removal and flushing off of any slots or standing lugs used for installation would leave you with nothing more than a fine ring at the muzzle as trace that you have inserts. One could even "age" the finish at the muzzle to make the modification even less evident. If all this is within reason, financially, I'd say go for it and use the gun as it was intended.
Merry Christmas!
Mark
