Secondhand boxes can be hit and miss. You can get a brand new one from the US for about $1600US but you'll need all teh conversion stuff too. They are available in all sorts of ratios too, even with an overdrive 3rd gear (like 0.85:1 or something on third, and the selector is just swaped over so it shifts in a 4spd pattern) - good when running 4.11's or the like.