[Shadowjack]

There's a limit to how narrow you can go with a rear before the tire hits the control arms or shock brackets. I imagine the vendor knows how far you can go, but I would ask them. I would get the narrowest one I easily could because all the neat rims are wider to the outside.
If you want disk brakes you need to address that before ordering the rear, so if it needs bracket work, they maybe can do that for you. There are several types and vendors for disk kits, but nothing really off-the-car in the yards, I don't think.