We just had our rear end fixed/bumper replaced on our '90. Parts were a b*tch to find and, not to dishearten you, the repair took over 4 months due to locating the parts. Ended up getting a junked rear bumper through Dino's Corvette Salvage in Florida and the shop had to repair the top panel damage. Some of the moldings were still available through GM and some of the parts came from White Racing. Good luck. Boy, do I sympathize!
The good news is that the car came out looking brand new. We had our repairs done through Purifoy Chevrolet in Ft. Lupton, CO.