A friend of mine talked about having put some "adjusters" between the rear axle spring perches and springs that can be adjusted with a wrench or socket to move the axle front or rear to correct the wheel alignment. I can't recall the name of them, but it might help you out in this case. It may allow you to not only set the rear as close as you need, but also custom fit for tire clearance if the driveshaft is long enough. Anybody out there familiar with these?