The stock rear shock towers are Ok, but the stock rear shock mounts are too small I think. They don't have a big enough surface area to distribute the load they endure under heavy use. The answer I think is to install some Ground Control rear shock mounts, they have a much broader surface area to distribute the load to the shock tower. They also use polyurethane bushings that will last the life of the car. They can also be removed from underneath the car so you don't have to pull your trunk liner out anytime you want to get at the rear shocks (adjustable Koni's ?).
Ground Control rear shock mounts
Mike