A gas turbine engine includes a compressor, a combustor, a turbine, a power turbine shaft, and a gas producer shaft. The compressor includes a compressor rotor assembly including a plurality of compressor disk assemblies. The turbine includes a turbine rotor assembly including a power turbine section and a gas producer section. The power turbine shaft is coupled to the power turbine section and is configured to couple to a first driven apparatus. The gas producer shaft is coupled to the gas producer section and the compressor rotor assembly, and is configured to couple to a second driven apparatus.