Our set of collarless 1:24,000 topographical maps are only available in NAD83.
If you need to use the images in NAD27, a somewhat crude but effective methods can be used to edit the .tfw world file. If you open the .tfw in a text editor, you can see the NAD83 registration coordinates for the upper left corner of the image. If you have access to methods (most GPS or GIS software) for reprojecting coordinates, you can reproject these coordinate values into NAD27 and then insert them into the .tfw and save the file.
