Raoul,
If you attach an earth lead to the terminal which holds the wires from the coil and condenser, you engine will NOT start!! :x
Early condensers were held by 2 screws but new ones with clamps attach with just one screw. You could use the second hole to attach an earth wire (using very short screw) or use one of the condenser clamp screws.
If the distributor does not ground properly, this extra wire will help. Benz Dr talked about this not long ago.
If your engine runs fine now, you will not notice any difference.
naj
naj
'Kloines Scheisserle'
65 230SL
68 280SL