I think the fiber washer and/or o-ring would be to seal the adapter to the case, while the flare itself seals to the high pressure hose (compression fitting)

Check out the pictures of this unit on EBay (especially pic #3 as it shows the threaded hole w/o the fitting).

http://cgi.ebay.com/ebaymotors/Mopar-Dod...=item3a5d5f3fe0

Rick Ehrenberg of Mopar Action fame occasionally would have for sale that threaded adapter on EBay, but none for the moment.