Stephen, it sounds like you wish to replace one bad barrel rather than the much simpler and cheaper task of fitting a set of orphan barrels to your frame. If so, it would be interesting to hear what Jerry Andrews thinks of that idea, and whether he gave you an estimate.
I thought about that possibility some years ago when I bought a 16 ga. G Grade Lefever that had been confiscated by a local Police Dept. The gun was stolen, and the crook sawed off the barrels to 9", making it illegal. They would not sell the sawed off barrels , so even sleeving was out of the question. I couldn't find a good orphan set, but found one with one damaged tube. So I wondered if it was possible to disassemble and then rejoint two good tubes. I never did find a second set of 16 ga. barrels with the opposite barrel I still needed.
I've never actually heard of anyone doing that, but it seemed plausible because there are some Lefevers that have two different serial numbers on the barrels, and the thought by some Lefever collectors was that some of them may have been returned to the factory to have a damaged tube replaced, and had the second serial number added. I can't imagine that would be a cheap or easy job, and would probably only make sense on a high grade gun, if it was possible at all. But with enough time and enough money, you could probably raise the Titanic, and get it sailing again.
eightbore was indeed lucky to find a perfectly fitting set of barrels for his 0 grade Smith. I lucked out the same way once with an orphan set of Syracuse Lefever barrels. The first time I fit a set of orphan barrels to a gun was also on a 00 grade L.C. Smith that I bought for $40.00 due to a blown left tube (obstruction burst due to snow). After several years, I finally found a good set that needed material removed to fit my frame. The other possibility is that material would need to be added to the hook by TIG welding or shimming. Of course, the width and height at the breech should match closely too, and firing pin separation has to be the same.
I started by carefully removing material from the hook using fine round files and round stones. I smoked the pin and hook and gradually achieved even better contact than the original set, but was still a little short of being able to close the gun. Then I made a real bonehead rookie mistake, and decided to remove a little material from the breech end of the barrels and extractors, never thinking that this would also make the rim recess more shallow, and affect headspace. I kept smoking the breech face and slowly cut-and-tried until I had good even contact at the breech and the correct clearance under the barrel flats, and finally the gun closed with that satisfying sound that a good tight L.C. Smith makes. I felt pretty proud of myself at that point. The top lever was right of center, and all seemed great until I decided to test fire it. I then found it wouldn't quite close with any factory loaded shell in the chambers.
I uttered a few choice expletives, and set the project aside, thinking about how I could cut the rim recess about .005" deeper to correct the headspace problem I had created. I didn't want to buy a reamer for one small job, so considered other options. A year or so later, I found a suitable milling cutter in a box of tooling at a surplus tool dealer, and altered it a bit by grinding between centers to get the correct 12 ga. rim diameter, and safely piloted to keep it centered in the chambers. I cut it by hand and finally ended up with a shooter with mismatched serial numbers. As I recall, my total investment in the gun, the orphan barrels, and the milling cutter was around $125.00... plus my time.
