lsd locking wont cause that as they generally break not lock, think its the lay shaft is fooked tbh
oh and the xr2i 16v box should fit but if its a mtx75 box ( doubt it though) then ya gonna have to use the drive shafts, the odd are its still a ib5 though
heres a strange one for ya alexzvhcabrio's longest lasting box for his car was a xr2i box
wierd or what