Re: Boilers

You didn't state as to what jusridiction is inspecting your boiler. The FRA has new boiler inspection laws that may be tripping you up. In the distant past, certain parts of boiler design were sort of guessed at. With today's technology, these stresses can be caluculated and what was a "guess" 75 years ago in now known for certain. Sometimes the answer is not what we want to hear.
Another part of the new regs bases the working pressure on what the boiler's current status and condition - not on what shows on the builder's drawings - and takes into account wasting of boiler sheets, rivets, etc. as well as any modifications done to the boiler.
What was perfectly acceptable before isn't necessarily so anymore. You are not alone out there. There are MANY locomotives out there facing challenges that will allow them to continue to steam into the 21st Century - including our Beloved K-36's.
About the only part of the SG 2-8-0 that became part of the 490's was the boiler. A new, longer smokebox was installed (to make the boiler fit the frame), but 497's boiler is NEARLY 100 YEARS OLD.
The longevity of a boiler depends greatly on how it is used but most importantly, how it is maintained and the quality of the water used in it. Bad water and poor maintainance will eat up the sheets and barrel quickly.
As far as replacing the boiler and destroying the historic integrity of the locomotive, I'll leave that to someone else to comment on.