5.7 Hemi into an old Suburban.

IMO, a hybrid would be the easiest. Using a stripped down 05 PCM to control the basic engine function and transmission. You would still need the VSS input for the trans. And the PCM would still regulate the alternator. The APPS would still be needed along with all the factory engine sensors. But sensors like engine temp can run off of a second sensor. Tach can run off of a spark plug. And you can see I'm in favor of analog gauges to eliminate any emission requirements. Now if you went with a A518 trans and run it as stand alone it really simplifies the PCM wiring. Anyway my two cents. Good luck..