Tailstock is #2 MT Headstock is #3 MT Per my 6" Atlas/Craftsmen shop manual. Atlas is still in business
http://www.atlas-press.com/servicebulletins.htm You can get a lot of info off their web site. A good source for tailstock chucks is ENCO at:
www.use-enco.com until 2/28/06 they are running free shipping....