A buddy of mine is an amateur drag racer. About two years ago he had his GM 10 bolt axle rebuilt with new gears and had a locking axle installed. I believe for parts and labour, it was around $ 1500 in total. They used quality parts.
It wasn't a dealership though, it was a performance car shop that does a lot of axle rebuilds, along with building performance engines, etc.
He figures he's had at least 90 + hard launches and runs down the drag strip with no problems. Also uses the car as a street car.
You might want to check with performance shops and gear shops, along with the dealer to get the best price....with quality parts.