I believe that the track can be widened by 2", however many might not realise that the track measurement is taken from the CENTERLINE of the tyres & not the outside edges.
This means that if the wheel is widened an equal amount in each direction, the track does not change. However, this is not what happens in practice. The additional width is usually added to the outside of the wheel & this results in that nice dish that we love so much.
If we widen our wheels outward by two inches each, & fit them to our car, we will increase the track by just 2"

What happens with many tub jobs is that the rear axle is narrowed to get silly sized wheels under there, & in so doing, the wheel track is often reduced, not increased. Particularly in those cars that have the outside edge of the rim in about the same place as original. This is need to allow the bag of the humungous tyres to clear the bodywork. It looks stoopid.

I was trying to upload a photo that illustrated this point, but still cant figure out how.
Chris