Lightroom :: Keeping Original File Name When Renaming And Converting To DNG

In LR 2.6, when I imported my images (RAW) I would import keeping the original file number, then I would batch rename and convert to dng after they were already in my catalogue.  Since I shoot stock, I keep a meticulous record of what I shoot for metadata and keywording purposes.  I notice that when I upgraded to LR 3, my in my existing catalogues/folders the original file names are gone, and just the new custom name & sequencing show up.

Unfortunately, I still have to keyword & metadata tag a lot of images, but now the original in-camera numbering is gone.  With my new imports what I did to preserve the original numbering, is to import, do my keywording/metadata, then a batch rename.  How to keep both.  It is just easier to refer to my notes when I have the original number of the image.