LETSRCE John if you are using lug nuts, you can get extra deep ones from a race shop. They will work but I would check the tork readings on them everytime you take them out. I don't know if you have enough meat to machine the 1/2" off of the center and still be safe. This is something you can't mess with. You better also check to see if the 1/2" is going to allow the tire to rub on either the body of the car inside or outside edge. It might be easier to just swap tires on the rims and balance them. You can get most wheels with and back spacing size you want down to 1/8". If those tires have been sitting for 6 years the rubber is harder than when new, unless you added a tire dressing and kept them in a cool dark area like the basement of the house. Wine cellar is a good place if you have the room.
Rick L