The factory shut-off valve is designed to thread into the water pump I believe?
https://www.flickr.com/photos/advance-design_parts_co/8377101217/in/album-72157631868452754/
I actually double blocked mine with a set of custom made valves.
https://www.flickr.com/photos/advance-design_parts_co/8129060091/in/album-72157631867396207/