then its just like subies. pretty easy to do, dependant on the setup of the engine.
eg, evos etc, come out east west, but are 4wd, however the 4wd gtr's are north south, s making them rwd would be farking easy, just a new box.
the east west ones, have a transfer case in the middle and shit, makes it icky.
you could always just remove the front half shafts
thats what u do in a subie... make it rwd by removing those shafts, and man... can those things drift
(note - the gearbox was never designed to send all 100% of the power to the rearwheels, so uh... subie gearboxes are already brittle... bye bye box
)