Here is one lovely L class old Fd lens from Canon that was sooo well done that was converted into movie camera lens by modifying the mount.
LINK
Not an uncommon story as I have seen many of these type conversions by Hollywood giants to take the advantage of excellent glasses. In fact sometimes back saw add on ebay that even would specify which movie the lens was used for...
Wonder why can't we convert them to todays DSLR mounts without obligation to use those unwanted converters with cheap glass that fully degrades the original lens' quality. Where is Don to come with some easy DIY suggestion?