According to the HZ parts catalogue there are four different rear stabilizer bars.

6cyl Sedan and Wagon
8cyl Sedan and Wagon
6cyl Panelvan, Ute, Cab Chassis
8cyl Panelvan, Ute, Cab Chassis

At a guess the 6 and 8cyl differences are probably due to differing shapes to fit Banjo and Salisbury diffs. Oz?????