It would have to come out of one end or the other. Try taking the nut loose on the end with the little black rubber thing and see if it is under that. I was fortunate enough to have removed one that was on a car with a recently (at the time) working brake system, and it worked fine. If there's a plug in the other end, take it out too. You might be able to work the shuttle valve back and forth and get it out. It's probably got dried out and stuck O rings.
Edit: Not sure if this is the video you saw, but it's the same K-H valve you have. If you can find a Cordoba, Magnum, or Charger from the late 70's, they have the same valve. You might get lucky if the still have brakes and they could have the 11.75 rotor brakes. All you'll need is the caliper brackets if your car is 73 and up. If it's 71-72, grab spindles and all for a cheapo big brake upgrade!