The key in the keyway is a half moon shape. I used a brass drift and a plastic hammer and tapped on one end of the key. That causes it to push down, lifting the other end. So I tapped on the side closest to the first bearing journal so the front lifted. Then using the same brass drift, I could get it onto the front that lifted up and tap it some more so it came all the way up and out.
I just laid the cam on a bench on top of a bunch of rags and then had my son hold it while I lightly tapped.
Using a brass drift works well on steel as it's softer so it tends not to damage the steel but will move it.