Complex sentence: Several prototypes were produced before the Frégate design was put into production: initially, the car had a rear-engined layout as in the recently launched Renault 4CV but eventually the manufacturer decided to go with an engine mounted ahead of the driver.
Split into simpler sentences: Several prototypes were produced before the Frégate design was put into production. Initially, the car had a rear-engined layout as in the recently launched $CV, but Renault decided to go with an engine mounted ahead of the driver.