the law is always open for interpretation, so take nothing i say personally. the problem with running an sr in america is epa never did emissions on the motor, so theres no base. for example its ok to put an lt1 into a camaro that originally had a 3.8 or put a 5.0 in a mustang that came with a 3.4, as long as the "bigger" motor was manufactured the same year or a later year as the original motor. and of course it has to have all the emissions bs installed that came with the "bigger" motor. whats really gonna cook your noodle is this, you can go down to the dmv and get an s13/s14 registered as an I-6 car if you put an rb in it. dont have any idea how that works.