This thesis is set in an ever-evolving industrial context, characterized by the emergence of Industry 4.0. It focuses on the FPT factory in Bourbon-Lancy (FPT-BLY), which specializes in the production of heavy engines for vehicles. The challenge lies in integrating the new XC13 engine into existing production lines while maintaining the current product manufacturing. This case study highlights the importance of industrial flexibility and reconfigurability to stay competitive. The main objective of this research is to develop an optimal method for implementing flexible and reconfigurable production systems in response to the challenges of Industry 4.0. Indeed, this industrial revolution brings new methodologies made possible by advanced technologies. The thesis focuses on the key aspects of Industry 4.0 regarding the system's ability to self-adjust and self-configure, which require significant flexibility to be effective and operational. The contributions of this thesis revolve around the identification, measurement, and optimization of flexibility in production systems. We have identified and proposed original individual measurement methods to evaluate different types of flexibility and have also developed a method to measure the interdependence between these types of flexibility. The aim is to obtain an aggregated value of the various flexibilities, in order to facilitate the prescription of an optimal decision in the event of system reconfiguration. Finally, we developed a mathematical optimization model to identify the best investment solution to achieve the appropriate level of flexibility and, consequently, determine the roadmap for deploying flexibility. We explored a large amount of data and company information for the experimentation and validation of these proposed models. Finally, all of these proposals were applied to the FPT-BLY factory, within the framework of the integration of the new XC13 engine.