The Multi Material Lightweight Vehicle (MMLV) developed by Magna International and Ford Motor Company is a result of a US Department of Energy project DE-EE0005574. The project demonstrates the lightweighting potential of a five passenger sedan, while maintaining vehicle performance and occupant safety. Prototype vehicles were manufactured and limited full vehicle testing was conducted. The MMLV vehicle design, comprised of commercially available materials and production processes, achieved a 364kg (23.5%) full vehicle mass reduction, enabling the application of a 1.0-liter three-cylinder engine resulting in a significant environmental benefit and fuel reduction.This paper describes the concept design, prototyping, and validation for interior subsystems of the MMLV. Case studies are presented for two of the interior subsystems: the instrument panel/cross-car beam (IP/CCB) and the front seat structures. Both of these concept subsystems are redesigned to take advantage of the weight saving opportunities presented by carbon fiber reinforced composite materials. Analytical methodologies are detailed along with prototype build techniques for each. The concept designs achieve a weight savings of 30% for the instrument panel/cross-car beam and 17% for the front seat structures. Physical test results are presented that validate the designs and the potential weight savings.