How can you tell the difference between a W50 and P51 gearbox. I know that they are both steel case, and that the P51 is close ratio, but how can I tell if the box that I have been given is a P51. I have also been given a diff by the same person, that I believe is a disc brake, live axle F series. Is it possible that they are both out of something like an RA45 GT? If they both came out of the same car, is it more likely to be a P51?