What model Cavalier in the 00-02's has the rear bumper with the cutout for the exhaust and would it fit on a 99 z24?
 
02's had an LS sport bumper that was basically a lip added to the stock 00-02 bumper.  I don't believe that lip will attach to a pre 00' bumper tho. 
However, the 00-02 bumper will mate right up with the 99', but you might have to a little trimming to the crushguard. You can get the stock bumper and then get the lip seperately, if you can't find it as a whole.  Hope this helps....
Convert 00+ headlights to 95-99