I have no idea if it's possible on a z20 but on my MX73 Cressida I used $2 D shackles and double mounted TWO standard rear sway bars. It made a MASSIVE difference. The second bar was mounted on top of the first bar and the link end bolts had plenty of excess thread to screw both on.
Tetsuo "King of the CheapAss Cressida Modders"
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