180. That alignment is pretty critical. The threaded hole for the front grip frame screw should be on the "bottom" while the valve output hole needs to be on the "top".
You do bring up a good point as well. While they should be in the right spot when the valve is tightened down it might be a good idea to put some alignment marks on the valve pieces before taking it apart. A line all the way down the valve would do the trick.