Bringing back an old thread but I follow Mike on instagram (Bluehandsvideo) and he has been sharing videos of his ball joint conversion for the 521. There was a group buy on a Facebook Datsun page that Mike mentions in this thread but it looks like he may have a few extra to sell. There are a few people on Ratsun, like myself, that are not members of facebook so I wanted to mention it here too. Check out Mike's instagram for the latest updates.