[turbohead7]

Any upainted part on the chassis or even a metal bracket behind the dash which is bolted or welded to the body is ideal. Remember, your negative battery cable goes right to the body. Battery voltage is best obtained at the ignition switch as FR stated, or from a BUS bar under the fuse panel. Or, an empty relay position will do fine. You can tap into the main voltage supply very easily behind the fuse panel. You don't have to be too concerned because you are wiring low voltage accessories with low amperage consumption. Always use a fused harness. You may even find an empty fuse slot, Or if you don't smoke you can use the cig. lighter slot. You can always tap off the battery, but it's usually sloppy looking and is subject to corroded connections over time, unless you use a gold plated connector available from car audio stores. When I 'm planning to run numerous accessories, I'll run a heavy guage battery cable into the car to an auxilliary fuse panel available with anywhere from 5 to 30 slots----based on your needs. But if this is all you plan to do---stick with the fuse block. Just don't steal grounds from other components. Always use a ground point with only a few wires on it, or you may have problems. Running your own ground point is usually best on all Porsches.