I recall reading somewhere that they were that same. But don't have that link.
But according to ADSITCO (my favorite parts store... Yeah right!
..... But I am sure their info is correct) the "Lower Control Arm- Rear" have the same part number.
W123
W126
And if you do a search on the Fastlane site, the trailing arms are the same part number.
So my guess it will fit and the Aluminum part is a nice discovery replacement for the rust belt folks.