[Roy Dennis]

Uninstalling and re Installing doesn't change anything because the data is in the kma and kmh headers.
Rebuilding the database doesn't renumber discs unless it finds duplicated Book or Disc Id's.

What format are they imported as KMA or KMH ?

With KMA the book and Disc Id is held in the KMA envelope, you can't change that without deleting it and re Importing it and that will only be possible if you have the original source or you convert them to zip as you suggested.

If they are KMH types you would have to delete all the KMH files along with the small text file that is in each folder with the source files but keep the source files.
Then re import them all.

I've no idea if that would re build them for you with the lower book id you desire. A lot of it depends if you import them with their original Disc ids or ignore that.

With imported CDs they normally have only 10 to 20 tracks per Disc and Book Id so that uses up a lot of Book Id's.
If you just import them direct from Hard drive but ignore Disc ID data then you can get 99 tracks per Book Id.
In theory that way you would be able to get 98,000 tracks using only a 3 figure route book id.

I think it would involve a lot of work.