[BigAls87Z28]

Then can because evey car off that chassis will have it. Economies of scale FTW. It would be more expensive to design, engineer, test, and certify a "bolt in" rear end that GM has to green light and warranty 100%, which would only make it more expensive.
Ford, on the otherhand, took an already paid for chassis, and ripped it apart, stripping everything. The cost savings per car for teh Mustang is about 300 dollars. The Camaro will come in at the right price point. Look at the LX cars. Full independent suspension front and rear, V6 and V8 engines, high tech gadgets....and they start at 23k.
It can be done, adn will be.