I don't appreciate the value of preserving internal elements such as iron boilers if it precludes returning the machine to operational condition. For instance, if someone came up with adequate funds, locomotives such as DSP&P 191 could be in motion again. Who would know if the metal under the boiler jacket was steel or iron? And of those who knew, which ones would care? Try to explain such subtleties to a typical visitor to the Colorado Railroad Museum and they will think you are mentally ill.
Wouldn’t it be nice to see such relics as V&T #11 and the like in operation again?
I bet in the year 2108 the entire fleet of K-36's on the C&TS RR will have 2nd or 3rd generation boilers.