Still looking into a kit car. Wife wants a Cobra and the builder (Factory Five) allows the use of an IRS and drivetrain out of the newer ThunderBirds. I also noticed that the same IRS also comes from a Lincoln. Not knowing if I'm going to increase the horsepower of the stock engine till I would see the performance in the lighter kit car. Should I serch out the larger rear end just in case I do increase the power or since it will be in a lighter vehicle don't worry about it? thanx in advance.