Found a ducati's website info about 851's. 888cc were made in 1990 due to WSB Homo. Earlier models were just 851 cc single seat's. 
  As per my 1989 851, the earlier 851's ran a different crack spindle for the sprag clutch. needed to purchase a monster one.  
http://www.mbracing.pwp.blueyonder.c...otorcycle.html.  
 
   £2500 - £3000 for the adverstised bike not £6k. 
 PS I'm still wanting a 851 someone most have one for sale below £3200