I bought 2 gtr boxes and a s13 box from jap import spares, anyway had then checked out quickly (read very f**king slowly don't get me started on these guys) by a gearbox specialist and one had some crunchy bearings in it, they swapped it over no questions asked, good service.
I have found generally they are priced quite cheaply, sometimes their new stuff is a bit dear if you know other places to look but other stuff i got from there is well priced.