I know a place in long island that does it, they did a fellow members car.
The only concern I would have is that after narrowing the axle tubes, the wider wheels will rub on the wheel well. I know of 1 person who put 12" wide wheels on his car, but had to grind off the protrusion perch in the well and also the shock boot.
I would check all clearances before narrowing the rear. There are a bunch of 10" wide wheels that will fit without any modifications.