Don't know, but . . . How much difference can it make?
The part is just two holes connected by a piece of steel with bushings. The distance between the holes is the same, no matter how the curve (if there is one on your parts) goes. As long as nothing is rubbing, it should be okay, right? And, If I was choosing, I'd install them the way the bolt heads are on the side with the greatest distance to the body of the part - assuming there's a difference. It's been a lonmg time since I did mine, so I don't recall the specifics.
Now that you bring this up, I need to do mine again.
1995 530iA - 295,000 miles
1988 325i convertible - 180,000 miles