Lamborghini created three pre-production Countach prototypes prior to the introduction of the LP400 production model.
The first prototype was the LP500, which was displayed at the 1971 Geneva Motor Show and later used for pre-production testing and development by the factory. This car had many mechanical and styling differences compared to the production LP400. It was built on a partial spaceframe steel chassis which was heavier and simpler compared to the production version's full tubular spaceframe. The bright yellow bodywork closely followed Gandini's original design for the car but was modified during testing with additional air inlets to improve engine cooling. The 5.0 liter V12 engine initially fitted to the LP500 was destroyed during testing and replaced with a 3.9 liter V12, similar to the engine used on the production LP400. The LP500 prototype was destroyed in a crash test at the MIRA facility in England to gain European type approval, even though its construction method was utterly unlike production vehicles.
Source: Wikipedia