I have heard of the big weal flanges on prewar stuff and does it apply to Fast track and modern O-27 switches? Is there a way to fix this if it is true? Thanks!
The problem with prewar on postwar O27, modern O27, or Fastrack switches is with many prewar engines, the wheel gear teeth run to the extreme of the flange and interfere with the switch frogs and gaurd rails. Same holds true with crossovers and Fastrack grade crossings. There is no easy fix. On some of the smaller 4 wheel engines, you may be able to change out the motor assembly with modern 4 wheel steamer motors.
Prewar O27 switches and crossovers will work with prewar, postwar, and modern O27 engines. That is probably the easiest choice.