Carburettor cars do suffer from carb icing. I used to have a zooped up mini (a proper one, not a small Bavarian) and on cold winter nights it was not unknown for it to suffer icing. In the end, I had to fit a water heated inlet manifold to cure the problem!
As for steam etc from car exhausts. This is simply water vapour that has collected in the exhaust system, especially the silencer, being expelled.
Simplified explanation... After the car is switched off, the exhaust is still hot/warm. As it cools, the vapour in the air condenses on to the surface of the metal. Then when you start the car, it is forced out as the "steam" you see on cold mornings.
Regards,
Shuttlebus