The A300-B4 was a conventional aircraft with steam driven gauges and a flight engineer, the later A300-600 had early generation EFIS similar to the B733 and did away with the flight engineer.
The first ETOPS regulations exempted aircraft with 4 engines or 3 turbine engines and date back to the Constellation and Douglas DC4/6 era. The Tristar and DC10 were able to comply, long range twins were a few years away. The early 1980s saw the B767/757 with transatlantic capability and the previous decades old regulations were bought into the modern age to cover this class of aircraft.
Now big twins such as the B777 routinely fly over the remotest parts of the world, hours from any suitable diversion and narrow bodies easily manage 120/180 mins, we’ve come a long way.