If I am interpriting what you say correctly, then I think that it could work. I am always a bit wary of epoxies due to temp and solvents (I am also a dinosaur !!) I think I would solder those bushes on personally. What are the thread core, OA and pitch of the threads on the barrels. I have the data for the Ruger ? Are the rim dia's of the two cartridges similar to avoid changing the extractor? Because the Ruger extractor is designed to move to the left for rimless cartridges then you will have some latitude here.
You have got me intrigued, I wonder if it is possible to make a stub bush for the #1 and fit a quick change pinned system for the change barrels. Intrigueing !

Regards