Maybe I am underestimating the difficulty of this project.
I was hoping I could do a lot of it myself. I was thinking once I got the barrel off I could either take careful measurements and have the barrel threaded to my needs or else just send the barrel I removed to whoever I get the new one from and have the new one milled to match. I wouldn't put sights or ramrod thimbles on the new barrel.
I know I could do the stock work myself and I have an extra laminated stock on hand that I would use. Then bed it and I'd be ready to shoot.
Am I oversimplifying this?
Art

Art - I really do not think that you are under-estimating the things that might need to be done. The other thought is that might even be able to sleeve your current barrel.

I THINK if

You took the old barrel off and sent it to whoever is making the new barrel, you could do the rest of the work yourself. It seems far less complicated than a bolt action and trying to get a tight head space.

I also think GM still makes a fast twist 45 barrel in 1-18 with cut rifling. It would need to be contoured unless you want a REALLY big barrel.

It sounds like Douglas can do almost all the work for you. Not sure about a breach plug though. http://www.douglasbarrels.net/pricelist/index.html

Turned, Threaded Cut to Length Crowned & Polished (FTC) $323.00