try removing the directory of the git repo that you are trying to migrate into from svn, or just move it out of the way:
$ git svn clone svn+ssh://firstname.lastname@example.org/path/to/svn/project/dir --no-metadata -T trunk /path/to/local/git/repo/project/dir W: Ignoring error from SVN, path probably does not exist: (160013): Filesystem has no item: File not found: revision 8481, path 'misspelled/or/invalid/path/to/svn/project/dir' W: Do not be alarmed at the above message git-svn is just searching aggressively for old history. This may take a while on large repositories
It doesn't appear to like having a poorly migrated git repo already there.
mv /path/to/local/git/repo/project/dir /path/to/local/git/repo/project/dir.bak