They were scrapped. The Corvette at the time had 315 HP. There was no way in **** that the Company was going to allow a non-Chevrolet motor to upstage their plastic wundercar, especially a V6 non-Chevrolet motor.
GM was originally set up on Division lines rather than platform lines like they are now. The Series 4 came at the tail end of the Division era so it was cancelled because Chevy didn't want it.