#5 & #7 Plugs on 340

I always use a piece of 6" or so vac hose and push it on the end of the spark plug. This is especially helpful when starting the plug because you can screw it in around corners without crossthreading.
If you make sure your threads are clean you just break the plug loose, slip this on the end and unscrew. Heck you could make it 2 feet long if you wanted to and do it standing beside the car.