As far as I am aware, there isn't a way to do it without using a backup from a stock phone... you can try a third-party recovery tool, but I can't vouch for any such tools.
Originally Posted by joshlogic
You can try editing the info.plist of your backup files collected via iTunes from Product Version 6.1.4 Build Version 10B329 to Product Version 6.1.2 Build Version 10B146... but I wouldn't recommend that except as a last-ditch effort.
These files are located at
on OS X and
on Windows XP/Vista/7. While the folder names and their contents are hashed, use the last date modified to find your particular backup (you may also note that the hashes of the folders are the UDID of the device backed up).