It is the 8-hole helix, not the 4-hole. As for being balanced, I don't believe it is, I bought it off of E-bay from a Polaris/John Deere dealer to use on my 800 chassis when I was going to put a mod twin in it.
I've since decided to put a w/c triple in the chassis, which most "been there, done that" guys seem to reccomend a button clutch for. There are some numbers stamped into one of the sheaves if you need more info, I don't have them available right now. Thanks for looking!