*This may help someone:

Horse I - 2 speed (1962 - 2/78 #314150)

Horse II - 4 speed (3/78 314151 - 9/82 634138)

Horse III - PTO (10/82 640000 - 6/87 856126)

Horse IV - OPC (7/87 858307 - and later)

*Exerpts from data at Troy Bilt Tiller Club over on Yahoo.

Much help is available at the Club:

Regards,

Ford