Involving a lot of engineering ingenuity, parts from different vehicles were joined together into contraptions being half-motorcycles, half-trucks, with remarkably efficient results. Soon, there was "production", with parts being more or less standardized. Progressively motorcycle parts were replaced by automobile parts, power most frequently being provided by Volkswagen air-cooled engines.
This involved a blend of engineering ingenuity, combining parts from various vehicles into hybrid machines that were half-motorcycles and half-trucks, achieving remarkable efficiency.  Eventually, production methods emerged, with standardized parts becoming more prevalent. Motorcycle components gradually gave way to automobile parts, with Volkswagen air-cooled engines being the most common power source.