A LS swap is one of the most popular engine swaps for performance cars as it offers a great balance between power and reliability. The good news is that, yes, a LS swap can run on just a stand alone harness. A stand alone harness allows you to use the existing wiring from your original vehicle while adding in all the necessary components needed to run your new LS engine. It eliminates any unnecessary rewiring or splicing into factory wiring which often creates electrical headaches down the road. This type of swap also makes it easier if you ever decide to switch back to your original engine since all of the components are already there and ready to go. With some basic knowledge, an experienced mechanic should have no problem getting everything connected properly so that it runs like a dream!