A 660 ultimow like this one???
Id say the pulley is the same as any of the Greenfeilds 28" cut mowers.
I'd say (hope) you're right - I was offered to take away a 28" ride on which we couldn't get out of the bog it was in, so pulled the engine off with the pulley on it

Looks just like the parts diagram
So did better than the measurements - got the pulley itself for the right price
