510 irregular rear tire wear

I have a 1972 510 that is probaly like most 72's(look's like crap, but run's like it's new). My rear tire's are wearing irregular. they wear out on the inside of the tire but are still like new on the outside part of the tread. I replaced the rear coil spring's and shock's not long ago. This did not solve my tire wear problem. It appear's that the rear wheel's do not have a negative camber any more. If i pry around on the control arm it seem's like there is some play in the control arm bushing's. Could bad bushing's be the culprit or am i barking up the wrong tree?