Rice Burner,
John you will find this varies depending on the train set from that particular era.
Your 731 freight set if I remember correctly was 027/0, it actually has the trucks to run properly on both tracks. The size of the rolling stock can vary, however what you need to really be concerned about is the min curve the rolling stock is designed to run on, rather than the exact car size. Some custom O guage rolling stock may very well be smaller in design than some actual 027 rolling stock, it all depends on the design of the individual car.
PCRR/Dave
