If you can source it, Canon did produce a "Mount Adapter E" which allows mounting Exakta lenses on any FD (maybe FL) body. But few FD bodies had mirror lock-up. It would probably take an F-1 or something, apparently you have an F-1n that might do the job. I have the more common "Mount Adapter P" which does the same thing for M42 lenses. See http://www.cameraquest.com/nikonaf.htm