You're right, it doesn't come with a drive pulley. The Baja Beetle one did and I assumed this one did also. You would need to get an FS30 thrust washer and use the groove in it to drive the fan belt. That's the setup I use, and it has never jammed the belt into the gears. The worst that can happen is if the fan pulley is not lined up right, the belt will skip off and you will lose cooling. In my experience, once the pulleys are lined up, the belt doesn't skip off.
I think the passive heatsink cooling is definately worth a try, but if I were you, I'd order a fan just in case since you won't be able to get one after they run out of stock.