You have a valid point, Haasman.
Indeed, when we embarked on looking for root of the problem, we started with the fuel system [from the fuel tank right up to the dividier and to the nozzles] - which is only logical. We thought it was a bad fuel supply from somewhere. When that was checked, we then went on to look at the air intake. Then, with the suggestions from our colleagues here, we looked at the sensor and ground although we didn't think it was that simple (we hoped it was, we really did).
Then we started with the ignition box when the problem persisted.
It was only that all else failed that we decided to check on the timing and noticed the distributor cap a little "bald" on the inside. On hindsight, we ought to have tackled this first.
Now, the car runs smooth.
In all actuality, it is very difficult to determine the starting point, and more so, which to follow next. Today's machines are not as straight forward as the 70's Datsun cars.
Anyway, the beer flows yet again, and thank you for your interest and support.