Please forgive me if this is a repeat, my previous attempt seems to have disappeared. 

I am working on a solution for our fundraising department to transfer data from our CMS to RE with minimal fuss.  I have basic Constituent contact info and educational info pulling in OK.  The trouble lies with the Phone import.  It seems that there have been 2-3 different procedures over the years each making different decisions about Import IDs, unfortunately there is no one still around to ask why certain decisions were made. 

I am typically pulling in up to 3 "phone" types at a time -- Home, Business and Email -- per constituent. For new records I was given specific parameters to build the AddressImportID (which I know needs to match the PhoneAddressImportID), and that seems to be working OK.   For pre-existing records, I do not have a predictable pattern of what the ImportID, AddressImportId or PhoneImportId would be.  At least one of the previous procedures had the system creating the IDs on the fly.  My matching percentage to update existing records is dismal. 

My IT brain sees 2 ways out: either I standardize the existing Import IDs (of various types) with the current parameters - Is there a way to do such a thing? Can I export the old ones, and re-import updated values?  (what would happen to duplicate address records? or phone types?)  -OR- I export all the existing values and put them in a table in my CMS, at least for the short term. {ugh}

Thoughts?  Other approaches?