It really is the same for PS-3 Steam upgrade. The harness and hardware are all the same, less the battery and battery harness. Follow the video and just stick to loading a PS-2 3V upgrade or PS-2 3V factory file for the engine you are upgrading and you should not have any problems.
People get into trouble trying to load PS-3 files. It wasn't really meant for that. It has been explained above. What works and what doesn't, and even why. G.