This paper describes a novel design and verification methodology used in the development of advanced combustion strategies for achieving 55% break thermal efficiency (BTE) as part of the US Department of Energy SuperTruck program. The tools and methods discussed consider spray formation and injection schedule along with piston bowl design to optimize combustion efficiency, air utilization, heat transfer, emission, and BTE. The methodology uses a suite of tools to optimize engine performance, including 1D engine simulation, high-fidelity CFD, lab-scale fluid mechanic experiments, and engine testing. First, a wide range of engine operating conditions are tested using 1D engine simulations in GT Power to thoroughly define a baseline; secondly,an optimization and down-select step is completed where further improvements in engine geometries and spray configurations are considered. Next, simultaneous high-fidelity simulation using StarCD and OpenFOAM as well as lab-scale unsteady jet mixing experiments are used to understand the interplay between fuel injection and piston bowl designs. Finally, a sub-set of promising designs are tested in an engine to verify model predictions. A key to the success of this design and verification process is the accuracy of both the 1D and high-fidelity simulations; these tools have been significantly improved and benchmarked against a range of engine operating conditions throughout the program. We conclude by outlining future directions for this methodology.