Firstly excuse me not to write about the Ambassador, its accident resistance and finally its perfect suitability for Calcutta. Please be fair to yourself and the newer cars in the market. So get a feel of what you would be surrounded with in a traffic jam. If at all there is any private car, chances are it will not be driven by the owner. People prefer keeping a driver.
Parking is very difficult.
You may visit NS Road for a task and return without it done just because you did not get a parking. Believe me, it happened to me. So if you have a driver he will somehow keep the car at some place while you get the work done. Also keep a driver as driving here is very stressful . Abrupt lane changing is the norm.