Mark VIII's, or Mark 8's. All the T-birds Cougars & Marks w/the IRS have that odd Volvo pattern, the Marks had Al-U-minimum lower rear arms & active airbag suspension, T-birds & Cougars had heavy cast iron arms & coils.
That's the one I took out of a V-8 T-bird, iron 8.8 3.27:1's & whatever limited slip name they used, I just broke it down last summer. Just the subframe & arms alone were 120#...