The Morgenthau plan, named after Treasury Secretary Henry Morgenthau, called for Germany to be stripped of its heavy industry as a way of permanently pacifying it. It was decided to not go through with it as it was deemed too draconian and would've caused Germany to starve and left in permanent poverty.
That idea was based on economic illiteracy. As Adam Smith pointed out, countries can trade so as to specialize in whatever they were most efficient at producing. Modern Germany happens to be very good at making cars, but not very good at making airplanes. So it buys airplanes from France and America and sells them cars in exchange. And so it would be if Germany was banned from having heavy industry.
Germany would specialize in light industries like electronics, appliances, furniture, consumer goods, pharmaceuticals, processed foods and beverages, and the like, and services such as banking and insurance. It would also export coal, coke, and timber. And it would import all the chemicals, steel, automobiles, aircraft, and aluminum it needed from abroad.
So, Daimler, Volkswagen, BMW, Thyssen, Krupp, Heinkel, BASF, Messerschmitt, and Junkers would be forced slam their doors for good. Instead, Siemens, Bosch, Allianz, Adidas, Bayer, and, god help us, Deutsche Bank, would make up the commanding heights of Germany's economy. Plus, there would be companies that don't exist IOTL specializing in the products that are allowed. Konrad Zuse created the world's first programmable computer in 1943. Maybe Zuse AG could dominate the computer market instead of IBM.
So really, Germany would still be prosperous and highly productive even with no heavy industry.