Yep back then nobody gave a crap about what model “Z” it was, it’s only in recent years that the first model Z1 has become so valuable. The truth is that the production company was loaned 10 new Z1000’s (KZ1000’s in the US) by Kawasaki Australia, most of which were wrecked during filming.
At the end of the movie the bikes were returned and Kawasaki Oz was so pissed off with their condition that they offered the bikes back to Bertrand Cadart who customised them for the movie and was cast in the movie too, for $5K, but as he’d only been paid $5K to customise them, he couldn’t afford to buy them, and he thought that he’d not make any money out of the deal anyway, who’d be interested in buying old movie prop bikes?
There were a few other bikes (including Z1’s) that were bought for the movie, and I believe (but don’t know for sure) that some bikes in the movie were owned by the extras who rode them in various scenes.