The only 721 I have re barreled was replaced with a 700 barrel. The relief in the stock for the swelling around the rear sight dovetail was not all that noticeable with the 700 barrel in it.
You can call Dan not sure he do the dovetail but gunsmith can do that and sights. You could send them the barrel and I think they charge $40/$50 or so and they match that barrel also.