You might be able to just install acs-tcl. It should not have any database upgrades, but of course, might expect some other code from 5.6 packages. It is worth a try though.
Overall I suggest you upgrade to 5.6 core packages at least. I am not sure what parts of core you have forked or what has changed but it should be possible to upgrade. That is the best plan if you want to use the layout manager.