I Imagine the only differces could be the hole centres for the corner of the radio tray and brake plate ,the corner of the carrier macined
to match the plastic v4 one and perhaps the bearing sizes .That sounds a lot but it isn't I have fitted a mk1 carrier and a mk2 (ultimate)
to a V4 and X4 with little trouble and no after problems . I did notice the first plastic V4 carrier has been Improoved ( My X4 one) is
much better with 4 screws and chassis lugs as well.