[FrodoGT]

Have you tried putting the car in gear with the engine off? All gears? If you can put it in gear and the car still rolls, Id say your clutch install has a hitch somewhere. Its pretty hard to break a ring or pinion gear on a stock powered car, it takes a few hundred horses to do destruction of that magnitude. It could be that the car isnt getting into gear at all, perhaps because of the linkage, or the selector. You need to try it with the car off, and try rolling it back and forth when its in gear. You will be able to feel the resistance of the gears even if it rolls, which would mean your clutch is not engaging because it is jammed up.