Is there a GM service bulletin out concerning this bushing replacement to be done on the early Z06's and particularly the C5's? If there isn't a manufacturer's document (according the solo rulebook) specifically addressing this bushing replacement on those early Corvette models, I believe that it isn't legal in stock class.
Bare in mind that the replacement bushing is dimensionally the same, but the bushing material is of a different composition and hardness. Street Prepared - Yes, Stock - No.
Someone correct me if I am mistaken.