I do believe I read that the OEM wheel offset is 30mm front and 50mm rear, that is with 6" wheel width front and 8" wheel width rear.
Of available aftermarket options, most typical offerings are 7" wide wheels, and a rare few (STI wheels like HD3) offer a 6"+1" offset, that 1" - 26mm (close approximation) the typical popular offsets are 5+2 & 4+3.
So best case scenario if using OEM width tires you might only narrow the front end by 1/2" overall and narrow the rear by 2.25".
If you add wider tires such as 30x10x15 etc. you will actually get wider that 68.5" not narrower.