Sorry if I'm a bit late on this, or it is a repost.
Over on flickr, one of the members of a group has created a bit of software which allows you to add correct EXIF data to scanned photographs (e.g. film, camera, lens etc).
Filmtagger is an application for those of us that still like to shoot film but use the computer to manage our photo collection.
Filmtagger makes it easy to embed EXIF, XMP or IPTC information in the scanned images about camera used, film, ISO, lens, date and other tags.
The program will scan the selected catalog and set the appropriate tags in all jpg or tif images it can find (a backup file will be created).http://nilemada.com/?page_id=166
Here's the link. I will give it a go later today, time permitting.