You can download the Husqvarna Viking 6440 / 2000 manual here for $4. In November 2016 I re-scanned this manual and meticulously created a PDF version of this manual superior to anything else you will find on the internet: full-color, compressed, print-ready, and zoom-able.
Also visit a great online (Yahoo!) group discussing pre-1980 Viking machines for even more information!
These are great machines.