That's gonna require someone pretty clever to re-establish the proper relationship of the underlug to the breachface of the barrels. That seems to me to be the difficult task. Figure that out, and the issue of the ribs is easy.
The entire barrel assembly needs to be fixtured or wired together during the process, IMO.
If silver brazing was used, refinishing will be required.
Just a thought, but
Dewey Vicknair
www.VicknairRestorations.com had posted some pics about how he built a fixture for holding barrels and ribs together during rib soldering. His fixture might work for this task. You might give him a try.
