Used to have a 1974 816 with the Onan CCKA, but sold it last summer after getting the Zero Turn.
I bought it in 2001 in NH. I had 50" deck, 44" snowblower (which is a cannon!), a Gravely tow cart, and a belly-mount grader blade. Having moved to MD, I no longer needed the other attachments and was using it exclusively for mowing ~2 acres (hence the switch to the ZT).
Loved my Gravely!