You can try to use the newer jars within the old jboss as by copying these jars to the old jboss as lib dir.
The conflict comes from compiling the sources for each appserver release (see serialVersionUID).
Thanks to sandor, but I can not modify the files in the 2 AS. What I need is making a client to call them, and I don't know how can achieve this by a single jbossall-client.jar. If I use older clientjar, I can't call newer EJB, and failed to call older EJB by newer client jar. :-(