I extracted the content of Update_Kindle_2.0.3.bin
Edited the 291330095-327610024.ffs script to simply do a "return 0) at the end of the code.
Edited the update-WebDownload.dat , change the md5 for the script, remove the reference to bundles.tar.gz
Then I tar/gzip all of this.
Converted the tar.gz with kindle_update_tool.py
Copied it in the Kindle USB disk ...
It took 10 minutes for my Kindle to restart into the Recovery mode (and the same error 003).
So I don't know if it's a coincidence, but the amount of time required to reboot got me worried !
going to play with the header of the package itself with the version required