That one sounds like a real jewel. You couldn't make me do anything to the original barrel. I talked with Stan Baker about installing screw chokes in mine, but he advised against it. He knows more about shotgun barrels than anyone I can think of on the planet. Cutting it off is a bad idea period. Reaming the choke out to a modified would work to some extent if it's done by someone like Stan. I found my extra barrels at gun shows and on ebay before they went Liberal.
I did quite a bit of looking around for a barrel for you but the only thing close is mine. They used to go new for around $180, but they seem to sell for closer to $300 with 3 chokes now, if you can find one. You might find a beater somewhere that has a decent barrel you could have re-blued for $35. It would make a good parts gun if it was the AL-2.
What I have is a like new Beretta Magnum 30 inch, Mobil Choke, Vented rib, 3 inch chamber, Matte finish, barrel with 5 Mobil Chokes. I also have a Browning B-80 2 3/4 inch chambered, 30 inch Std Invector barrel with 4 Briley X2 Chokes that I use for hunting and clays. I don't like and can't use 3 inch shells, so I might be tempted to sell the Beretta barrel or make you an offer on your AL-2. Do some searching and see what you can find and get back to me.