Thanks. The trouble is that I need a definitive statement from someone who the DVLA will accept, e.g. Ford - local garages say they don't have records for that long ago, a garage/mechanic - they don't seem to want to put their name to a document unless they can also find something definitive online, which confirms block numbers to CCs or maybe a car club statement on headed paper would do - I don't know who to ask in the RHOCaR.
Basically I don't want to open a can of worms with the DVLA, by which I mean if I tell them correctly that it is a 2 litre but cannot back that up if they ask questions, then I don't know what action they may choose to take (if any), e.g. insist on a report that I can't yet get.