Try our new info resource - "Aladdin's Cave" (Main menu)Just added a separate link to Ash's Dropbox thread (shortcut)
Both will work, maybe they were different for different countries. UK 400's were singles
My UK 400 had one earth nut on each side as does my 500 - my parts book also shows Qty 2.IIRC each wire had a connector not two into one.