Sunset has been around since the 1980s or earlier. Scott's father, Mort, started the company. I don't think they did much in 3 rail back then. And everything was brass.
As for radius, unfortunately if you want somewhat accurate models, rather than toys, you are pretty much stuck with larger radius, especially with steamers. With 4 axle diesels, you can usually run tighter radius.
A lot of the smaller steamers will work on 072 or even a little tighter. I have not heard of one that will go around 031. A friend of mine has an OMI 2-8-0 that will happily go around 072.
Sunset over the years has imported many, many steamers of all sizes. I have steamers from back the early days and a most recent PRR L1 mikados. This L1 came factory painted and is the most detailed loco in my roster. It is also a very good runner as is the PRR N1 2-10-2 from at least 15 years ago.
