There are two ways to find the software versions usable via the ilcdirac interfaces
Use the script: dirac-ilc-show-software that dumps the current available software.
Or look in the configuration system:
https://ilcdirac.cern.ch/DIRAC/ILC-Production/ilc_user/systems/configuration/browseRemoteConfig
Operations -> Default -> AvailableTarBalls -> x86_64-slc5-gcc43-opt -> Application
In the Configuration system you can also hover over tarball option and see the comment for the application version.