@kgdjpubs posted:By and large, the outside is just window dressing. When you take them apart, it's all basically the same thing. There really aren't many "special" parts for a specific locomotive any more for the later engines compared to the earlier engines. It's still small quantity custom orders for renewable parts. The tolerances will change from engine to engine regardless of when it was built or its size. In the big picture, firebox work is firebox work. Boiler work is boiler work. Running gear work is running gear work. Appliances are basically the same--air pumps and injectors are basically air pumps and injectors.
There is a little bit of a difference in construction techniques and a few modern things when you are going from basically World War 1 era designs to 1940s era designs--welded boilers vs riveted boilers, superheaters, differing types of valve gear, dealing with higher boiler pressure.
There's just more work on a bigger locomotive, but if you can do machine work, you can restore a bigger engine just the same as a smaller one. Just be prepared to write a bigger check.
I understand the machining bits, but I would say the hard part is finding someone to do what is needed. Not many places where they would be willing or able to make certain parts. I know price will always be one of the big obstacles.
