A new car could be retired using one of the aftermarket wiring harnesses made for racing and classic car retrofit applications. You could probably splice in most of the accessories, but the real problems are the throttle-by-wire engine control and the fact that many safety inspections now include plugging into the OBD scan port. If the car won't "talk" to the state's computer, it won't pass the inspection.
There may be some loopholes in state laws, but this stuff gets tightened up each year.