Rear end not centered

I heard it mentioned from another member that a lot of rear ends are not centered on Chrysler cars, and could be off quite a bit. I just checked my fender clearance on my 73 Duster, and the left side has about 3/4" more tire clearance than the right side. My 74 Dart was also off center. Can this be adjusted? This would make buying the proper rim and tire size very hard. Any one run across this? :?