I would use 2 methods.

1. Restrospect and maybe a DDS2 or better DAT drive to backup the HD to tape. You will need a working OS and Retrospect to restore the files if/when the HD needs replaced.

2. Setup a PC server with Win2k (virtual win2k on Win7/8 should work as well) so that you can have apple shares and dump the files to the server for storage (and whatever backup method you prefer).