This paper discusses the packaging characteristics of a family of power-packs for military land vehicles in the 21st century. 3 classes of vehicles are considered: light vehicles (300 - 600 Hp), medium weight vehicles (600-1000 Hp) and heavy vehicles (1000-1500 Hp). The paper highlights that a common bore engine approach provides both very good performance and a very compact power-pack. 2 different engine styles are examined. The results are expected to be applicable for a spectrum of modernized engine platforms that would employ a common bore engine approach. The approach offers many product development and production advantages, including lower development and tooling costs, and reduced product inventory needs, lead times, development costs, in addition to reduced product development risk. Various trade study parameters are considered in addition to engine power. Power-pack configurations based on a common bore approach shows significant commonality advantages and manufacturing efficiencies across the future family of engines horsepower classes. The common bore engine approach also demonstrates that a significant reduction in power-pack space claim can be achieved, while still retaining all of the development, production, and, maintenance advantages