Surprised nobody mentioned Speedwitch, assuming Scott wants HO. They would be the definitive set. I understand they're now available form National Scale Car. The Microscale set for Fowler boxcars is a decent workaround for roadname, slogan and monogram with a bit of cutting and piecing due to the different framing, but will need appropriate dimensional data. I went that route in O scale some years ago. AFAIK K4 has not produced any CNW decals. (Yet?)
