Which company constructed the Countach LP400 chassis?

The company that constructed the Lamborghini Countach LP400 chassis was Marchesi.

Marchesi, a specialist manufacturer based in Modena, built the tubular chassis before it was transported to Lamborghini’s Sant’Agata Bolognese factory. There, Lamborghini workers assembled the car, installed the engine and transmission, and completed the paintwork.

The arrangement can cause confusion because several famous Italian firms contributed to the Countach. Bertone was responsible for the striking body design and bodywork, while engineers including Paolo Stanzani and test driver Bob Wallace helped develop the car. Dallara, another important Lamborghini engineer, is therefore associated with the project but was not the chassis constructor named in this question.

The LP400 was the first production Countach, built from 1974 to 1978. Its name referred to the car’s longitudinal rear engine layout and its nominal 4.0-litre class, although the V12 actually displaced 3,929 cc. Lamborghini produced 157 LP400 examples before introducing the wider-tyred LP400 S.