This is not an easy project and should only be tackled if you are an experienced modeler. I never finished this project and don't recommend it. It is way too much work for a single caboose.
The C-26A, C-27 and C-27A classes of caboose are essentially identical. This project can be used for any of the three, but is labeled "C-27" here for simplicity. The C-26 and C-24 have different physical features and will not be covered in this project.
The C-26A class came in B&O road numbers
The C-27 class came in B&O road numbers C-3925 to C-3986.
The C-27A class came in B&O road numbers 904000 to 904093 and C&O road numbers 904094 to 904159.
Below is a prototype photo of a C-26A class
by two C-27 or C-27As.
1. Purchase a Walthers International Bay Window Caboose. An undecorated kit would be preferred, but I could not find one and started with a Chessie decorated one. Disassemble if you are not starting with a new kit. Set aside the bottom frame and trucks.
2. Carefully cut out the sides. Sand smooth, leaving just the roof and the ends. See photo for clarity.
3. One of the two end windows in a C-27 needs to be filled. Fill the one farthest the small vent pipe on the roof. I used sheet styrene and sanded it smooth. Be patient. This step will take some time.
4. Shave off the mounting point on the roof for the smoke stack. It is on the wrong side. Put it in the same relative position on the other side of the cab (the same side as the vent pipe).
((This is where I am now))
Below is the caboose I used, halfway through
Save the bay window, it is good for a C-24 caboose.
Below is the caboose with the sides off.
and ends still needs to be sanded square and smooth.
Below is the end with the window filled and