MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.
I will grant you that...IF you are printing rolling stock and IF you are also printing the bogies for them.....however, given the quality that I have seen on here for 3D print trucks and wheels and the fact that the wheels would be plastic, I can't honestly see why you'd want to. I think it would be far better to use commercial trucks with metal wheel sets.
Given that, I stand by my comment that all you need is the percentage, whether you are scaling Scale, or Gauge.