Projection mapping (PM) is useful in the product design process, since it seamlessly bridges a physical mockup and its digital twin by allowing designers to interactively explore new textures, colors, and shapes without the need to create new physical mockups. While PM has proven effective for car interior design, previous research focused solely on supporting the design of dashboards and instrument panels, neglecting evaluation in realistic driving scenarios. This paper introduces a self-contained car interior design support system that extends beyond the dashboard to include the A-pillars. Additionally, to enable designers to evaluate their designs in authentic driving conditions, we integrate a driving simulator, complete with a motion platform, into the PM system. Through the construction of a prototype, we demonstrate the feasibility of our proposed system. Finally, through user studies, we derive guidelines for PM-based car interior design to optimize the user experience.