Spark plug question

If the question is whether you can use either 5/8 plugs or 13/16 plugs.......the answer is yes, as long as you choose one with the correct length (thread reach), heat range, and sealing configuration. If you pull out incorrect short reach plugs, I would run a thread chaser tap into the hole first to clean out any carbon build up before installing the correct long reach plugs. Otherwise, they may not seat all the way in and work themselves loose, or, they might jam so tight they might be very hard to remove at a later date.