Ok. so in between drinking and eating this weekend I managed to do a bit of work on the old girl.I fitted the new speedo cable and 3.7 drive cog.

Of course it wasn't as easy as I was hoping.The speedo cable exits the firewall right behind the brake booster.
It was either take the booster off or try and manouver the cable up behind it.With the use of a bit of fishing line and a little help from the ball and chain it eventually went in.
Looks like the handbrake cable has been rubbing on it for the past 37 years