It looks like for series 2 GTs cars, the wheel is screwed/bolted to the boss and on my car at least the heads are ground down, so no way of separating the wheel and boss without some major machining. Much to my surprise, I read about it but never tried it, the boss/hub slides up and down on the steering column spline to adjust the wheel distance, so removing the circlip lets the wheel and boss slide straight off.
Plus few pictures of before and after of the wheel.