Just a though - if these are 32bit or 48bit not gamma corrected files right from the scanner (I guess through VueScan or Silverfast), why don't you save them as DNG files? You would save yourself all the hassle, since all the info including from ACR and IPTC would reside inside the DNG as it should. And they should also get associated with same name JPEGs, am I right, Kirk?
I am pretty sure both scanner software allows output to DNG.