A method is disclosed to enable the efficient physical packaging of gas turbine engine components to optimize power density, more readily integrate with other equipment and facilitate maintenance. The method illustrates dense packaging of turbomachinery by close-coupling of components, and rotation of various engine components with respect to engines and/or other engine components, and reversal of spool shaft rotational direction to suit the application. Engines can be dense-packed because of a number of features of the basic engine including the use of compact centrifugal compressors and radial inlet turbine assemblies, the close coupling of turbomachinery, the ability to rotate key components to facilitate ducting and preferred placement of other components, the ability to control spool shaft rotational direction and full power operation at high overall pressure ratios.