#58 was a steel mill loco. The guy who owns and rebuilt it runs a steel mill museum. So yeah the rail is over sized. Usually a loco frame is 2 slices of steel spaced apart. This loco is solid steel between the wheels. He nicknamed it the rolling ingot.
Oh and it never had brakes on it. But he is fitting 2 small air cylinders under the steam cylinders to push brake shoes. Currently braking is done by reversing, just like it was done years ago.