Have a look at this article:
http://msdn.microsoft.com/en-us/library/ms143241.aspx
One note from the article:
Because the SQL Server on-disk storage format is the same in the 64-bit and 32-bit environments, a replication topology can combine server instances that run in a 32-bit environment and server instances that run in a 64-bit environment.
Bye!
André CR