[kdbolt70]

Many of those regulations are there for a reason. If your car's suspension, crumple zones, and frame are designed to support an LS3, just throwing an LS7 in there may have adverse safety effects. Therefore, the entire car would need to be tuned and retested, it is a safety thing. Not to mention different exhaust and emissions. They'd have to sell it for quite a bit more to recoup their development costs, and have to deal with the tree huggers already gunning for GM's head.