easy way? that involves buying another custom wheel. i was hoping for an answer like, there's an adjusting point on one of the leaf spring mounts. can it not be fixed?
I would say that you need to measure both the body and frame... and see where the discrepancy is first.
Was the differential centered before you did the bushings ?? Do you know if the car has ever been in an accident ??
Looking for the "easy way" doesn't necessarily mean the "correct way" to solve your issue. I would not recommend moving the spring perches... nor would I ever recommend using a different offset for a single wheel... those are just band-aid fixes that do not solve your issue.
moving the spring perches is a perfect way to solve the issue, assuming they were welded in the wrong place, It, huh, happened to this guy, huh, I knew once, yeah something like that.....