There should be no incompatibilities between various versions of AppleTalk.
It's important to know that AppleTalk phase 2 was introduced with AppleTalk
version 53.
AppleTalk version 56 introduced many bug fixes and should be the minimum
version in use on any network with highly utilized servers or routers.
Most of the bug fixes included in version 56 were related to crashes and
other problems with nodes operating in a high stress environment.