brr: I found the caboose plans right off (for a change). They are in the July, 1966
Model Railroader. They are in HO, but Staples will blow the copy up 1.8XXX to O
scale. I can mail a xerox to you gratis, for your mail address. That is not the only
place I have seen them, either. Just first found. I don't know if the Colorado Midland
Quarterly, edited by Mel McFarland of Colorado Springs, who wrote "The Midland Route" book on the railroad is still published...(you might find out by emailing the publisher of "Narrow Gauge and Shortline Gazette"), but that quarterly had plans for the caboose and other cars periodically, but usually in HO. (that book has drawings of four different variations of the caboose, plus assorted other rolling stock, passenger cars, etc.)
The hopper I have, along with a D&RGW, one is IM, I do not have the Huff and Puff
boxcar, but the gondola I have is probably H&P. While I have ignored the single door
Weaver reefers, I have seen photos of single door reefers operated by the CM, as
well as the famous double door Pullman Hanrahan car. The McFarland book has drawings, just outline drawings, of all of these including the Hanrahan double door reefer, but there is a photo of the reefer in the book, too
The MR plans are of cabooses 401-416, the first series of side door CM cabooses (with
the reverse curve roofed cupola), built by St. Charles Car Co. I have several freelanced side door cabooses with that cupola, but have not done an accurate scale
model of a CM one. (as usual, I think there have been HO brass ones and kits)