There are several problems with what you want to do. First off, you can share NTFS partitions, but most linux distrobutions cannot yet write to NTFS partitions accurately. You could allow the users to copy off of the NTFS drives, but you cannot allow them to add/change anything.
You could make 3 directories within the ftp directory, and then mount each of the drives to one of the folders. You would have to be careful with the permissions if you do this. You'd have to make sure the ftp user can write to the directories, which isn't the default way drives are normally mounted.
Should be easier to convert the drives from NTFS to FAT32, as it is easier for the linux to write to that filesystem, and windows can still see and write/write to it without 3rd party programs.