Atwater Ca. 95301  about 2 hours south of Sacramento. 

The Thiry's my neighbor used and later were given to me, now passed to new owners, used the belt pulley with the long shaft.
I was always told not to misplace that coupling.
The pulley attachment was always used on the "sidewinder" (orchard seat) Thirty's and pulley was at some point rebuilt much larger, about 18" in diameter. NO SEAT, so when the pulley was on it, it was very wicked to move, I was never allowed to help move it with the pulley on, I was a teenager at that time.
used to pull the belt driven well pump.

I am not sure but think that pulley would also fit a Sixty.

The only differences in the Orchard vs. Cruiser was the transmission cover. Was not difficult to convert one to the other.
CTS

Yes I am sure that spinning pulley under the seat would have had your full attention. I can’t see hoe the pulley would work on my sixty unless there is some adapter that I am missing.