Across the rear wings, but the spinners may protrude further. My second garage is critical on width, which is why I went for a narrow Plus 4. (4/4 body & wheels with Plus 4 running gear).
As said above, some Plus 4's came with optional alloys so the width will be different than with wires.
Some Plus 4's were specced with Roadster wheels and wings, which to my mind adds too much weight for the 2.0L engine. Again, optional alloys or wires will have two different widths.
As far as I know, the later cars all shared the same body TUB width, I suspect from soon after the long door upgrade, but I would have to look that up.
