Rear Alignment problem on Mercedes 250
 

I have a customer who has a 1972 Mercedes 250 which is severely wearing the left rear tire off on the inside. The Michelin tires have less than 2500 miles on them. It has worn the tire right down to the wear bars on the inside and the outside of the tire is like new yet. The tires have never been rotated, so it's not a case of that particular tire being on the front, where it could have been damaged by a front alignment issue. When viewing the car from the rear, you can see that the left rear tire is tipped in to the inside. However, the car does drive fine with no noticable steering or suspension issues.
I checked the bushings on the left rear control arm and they seem to be fine. Although there is no visible damage, it appears to me that the control arm itself is bent. I know that it is not a matter of rust weakening the control arm---this 250 has always been garaged and it has only 67,000 miles on it, so everything is structurally in good shape, on the underside. I checked with my front end alignment guy, who looked it up and said there is no adjustment for the rear alignment on a '72 250.
Has this ever been a problem with the 250's and are replacement control arms available?

Anyone?