Considerable effort has been devoted to the modeling of proton exchange membrane fuel cells (PEMFCs) as well as fuel processing units (FPUs). Many of these models consider only steady state analysis; the available dynamic models typically operate only in simple open loop configurations. However, a liquid fuel processor/PEMFC stack power unit for vehicular application will require tight integration and regulation of multiple units in order to function economically and reliably. Moreover, vehicular operation is inherently dynamic in nature, so traditional steady state process design approaches will be of limited value. This work addresses a minimum set of subcomponents necessary for modeling an overall vehicular power system. Additionally, the integration and control of these sub-units is addressed so that the unit can be operated as needed in a vehicular application by following a reference power trajectory. A number of design and operational parameters can be adjusted and the impact on system performance studied. Based on this preliminary analysis, heuristics are developed for optimal operation and design.