Try our new info resource - "Aladdin's Cave" (Main menu)Just added a separate link to Ash's Dropbox thread (shortcut)
That type of plug cap was also fitted to the Opel Rekord (D) Coupes back in 1973 I was drivng one down to Cornwall for our sumer holiday when the car dropped onto 3 cylinders in heavy traffic. Being an automatic it was it was almost undriveable.One of those caps had failed plus the leads were the then quite new carbon fibre typ leads - I used a Nappy pin to replace the cap - it worked a treat.
I was told they were used to surpress radio interference back in the day.