Where can you find new cones for a 7.5" 10 bolt posi unit? Took one apart to inspect it and one of the cones is cracked, other then that it looks good.

I have no idea what year or what it is out of. The case doesn't split in half, but their is a cap on one end that comes off, it is held on by 5 torx headed bolts.
http://www.chevelles.com/forums/olp/images/misc/progress.gif

That is an Auburn. They are not rebuildable. The only parts that I know of that you can get for them are the springs and plates.