I did some framing work for Shelly Katz on some civil war pics produced from original negatives in the Smithsonian and you might consider his process. Scan the originals, put them back in a safe dark archival storage place and do all the touch up work in Photoshop.
Cheers,
Mark
http://www.pbase.com/lila161
http://blog.framedestination.com/
