LS and B16 are the same and gsR and ITR are the same, i know that an ITR diff WILL fit in a B16 , most people said it could but you do have to do some slight mods internall to the tranny. i had an ITR diff in my gsR tranny and i dont remember us doing anything special to it.

i know they are good diffs, this one in particular held over 300hp forever, and i never broke it or anything i just got a different one.