There's also this to consider (from the tfw boards)

Prid Cliffjumper's head is a "male" balljoint. WfC Cliffjumper's head is a "female" ball-joint socket. So it will not fit directly.

I haven't confirmed this myself, but if accurate then that means the Prid head plugs into the body, but the WFC head plugs on to the body. It'd still be possible to do but would need a bit more work.