Actually, the most significant change was the washable plastic inside roof lining after the plant vacation shutdown in 1962. Earlier this was a rather, fluffy fabric coating. Then the introduction of the so-called fresh air heating system was much more important around turn of the year 1962/63.
To date, the engine cooling air left and right at the exhaust manifolds of the both front cylinders was heated additionally and sent into the car interior. Even at slight leakages could be contain exhaust and oil mist parts, which were able to endanger the health of the occupants.
Now, about 15 percent fresh air was diverted left and right at the stationary cooling blower clearly visible hoses (Picture 4*, red arrows) after opening of the hood and heated only by 'heating bulbs' (Picture 4*, blue arrow) called heat exchangers on the exhaust pipes.
For this, the from the front two cylinders coming exhaust pipes were casted all around with ribbed light metal in its straight part back, where was guided always increasing warmer fresh air in counter-current process. If the heating is turned off, the heated air is directed before entry into the interior to the outside. 01/15*shown on a more modern engine