Posting this for a friend.
This may be a bit of a long shot but he is looking for an air cooled Suzuki RM400 motor. I believe they were made from 1978 to 1980. Stuck is fine, he already has spare pistons and what not, but cases need to be in good condition. Its for a vintage MX bike he is restoring.
PM me and I'll put you in contact.
Thanks for looking