There was a change to the pto pulley size starting in 1992 (Ser# 821,060 and above). The ones after that date are 6" and the ones built before then had the 4.6" pto. I also think (not 100%) that the ones built after 1992 are the yellow decks(Cub built) and the ones before are the white ones built by Haban. I would think that the yellow decks have a larger center pulley to keep the ratio the same. I have both decks but can't get to them right now.
