Looks to me like a job that will involve lots of time and money to do. I suppose the barrel could be cut off at the receiver, then bored out by a mill or lathe. After that's done, I recommend threading the receiver and new barrel for a nice custom fit.
I have worked on a few and the idea of removing a pinned barrel would be a awesome task. Just removing and replacing a new front sight took a helluva lot with a BFH to get off and that was with heat. I'm beginning to think these guns are made while hot , then all press fitted together, afterward, heat treated.
just curious, how do you thread a receiver and barrel when they are almost the same size ? i wouldnt think there would be enuff metal to thread .