Good luck. They will either come off in 20 seconds or you'll lose a finger trying to get them off.
There's a retention clip that you press to release the headrest. The clip presses into the stops to hold the headrest at a given height.
Some folks have used a hacksaw blade down the backside of the headrest (from the top). I couldnt do that and had to unzip the seat and reach up the back of the seat with a screwdriver. I accessed the clip deal this way.
If a donor car is a vert, good luck. That's the part about me about losing a finger. The metal rusts together and can be a real PITFA to spread apart. I spent an hour on one headrest and 1 minute on the other because of this.
Good luck.