Watford Cheeta 1962 Tachometre similar tha Anglia

Hello Everyone, 
 
I'm busy by restoring a Watford Cheetal 1926. Engine is an HP 15 Ford from the 50s.
Like on For Perfect or Angla
I have no Tachometer cable.
Just two questions :
 
1) Where do I have to plug it.... on the engine, gearbox, alterno ?
2) I have a tachometer Smith and son with a unsual plugin system... Where May I find a cable?
 
Happy to have the feedbach from a specialist 
BR
Cédric