K-37's

Another Thought.
When the K-37's were created from the boilers of the C-41's (?) were the standard gauge engines already out of service(dead lined) or were they withdrawn from active service? How many of the standard gauge cousins were still operating and when did the last leave service? I know ther are few photo's of teh standard gauge engines and theat they were were pretty ugly but I know little else about them. They seem to be sort of a shadowey figure. Perhaps if I research La Massa's book I could find some of this like when built and when converted but I am not sure about the retired status.
Just wondering
Frank