650 sprockets will work. But dude, I have one (JT) brand new I'll send you, just pay shipping. The eBay listing was mislabeled, I needed a 520 but it's a 530. Didn't feel like returning it.
One thing is that I did some lathe testing on it, which failed completely. It has marks where my carbide tool skated across the face but didn't remove any material. Still %100 functional and case hardened. PM me your address if you're interested, I can ship it out today.