As stated above It is usually cheaper to sell that barrel you have on GB and buy what you want if you are not doing it yourself.
I have cut many of them for people and some just wanted an 18.5" defense barrel or a 22" deer barrel. Just measure the OD at the point you want it cut and you can determine if it can be tapped. Some just leave them with the cyl bore as they work great for slugs and BuckShot that way But not much good as a turkey barrel
I measure and then cut them even with a rib support then, if not threading it, "crown" the barrel and re-blue it to prevent rust. the bead is the easy part and takes all of 5 min to drill and tap for the bead. A smith has to do a few just to recover the cost of the tooling. Taps and reamers are about $90 each Plus all the pilot bushings to match the barrel ID (inside dia.) which are only about $10 each but there are about 20 of them. not to mention a lathe which he should have anyway.