http://custom.simplemachines.org/mods/index.php?mod=2507New options added in "Administration Center > Forum Maintenance > Members > Reattribute User Posts":
Option to reattribute all guest posts regardless of username or email.
Specific posts to be reattributed based on post ID. Default value is all posts.
Define how old (with age or date) posts should be, in order to be reattributed to the registered member.
Posts can also be reattributed from registered members instead of the default option to reattribute guest posts only.
tested and may come in handy one day.