Carlson's Choke Tubes out of Atwood, KS was recommended to me by most of the CASS shooters, and they did an awesome job on my Winchester '97. I sent them the barrel and had them cut it down, thread it for tubes (2 or 3 tubes and the wrench came with it) and install a brass bead.
Can't remember the price for the life of me, but it's on their site; very reasonable.