The smaller and earlier Rail King line usually ran on O27 curves. This includes the early F3, the 2-6-0, 2-8-0, 4-6-0, and the General. Buy from a dealer who gives return priviledges or has a test track. Make sure you test against your O27 switches. Many cars and locos will go around O27 curves will hit the O27 switch mechanisms. The now hard-to-find KLine O27 switches had a very low switch motor, and was therefore the preferred solution.
Since MTH came out with their own O31 track, they didn't bother testing for O27. So again, you'll have to do your own tests.
my thoughts, your choices
