The BMW 3, 5, and 7 Series of the late '80s have semi-trailing independent control arm suspension. This suspension appears to be about as simple and lightweight as practical. The lower control arm entirely locates the hub for correct geometry, the coil-over strut/shock does not serve to locate the suspension geometry.

A lightweight steel tube transverses the width of the car, it is attached at two points to the unibody structure perimeter. The tube is approximately 3" near the permimeter, it enlarges and forms a 8" donut at the differential housing(the driveshaft passes thru the donut). The diff attaches to the donut. There is a small rubber damped mount in the top of the alloy diff housing. As far as I could determine this afternoon, there are only 3 attaching points to the rear suspension (other than the coil-over struts).

The unibody of the BMW is similar to a Mopar. The BMW drive shaft appear to be unlike U.S. cars. Other than the driveshafts it appears that the BMW might adapt relatively simply to an A-body. The 3 Series is a similar design to the 5,7 Series but is lighter and not as wide.

My analysis was made at the Pick-N-Pull where there are a half dozen of these BMWs. I haven't seen a rear suspension design that is simpler or lighter. In contrast, a late model Ford Thunderbird/Cougar IRS has heavy cast iron trailing arms and multiple attachment points). I believe that if you cut the cross-member tube towards the driveshaft (inward from the trailing arm pivots), you could widen or narrow the tract width without affecting the geometry.