SODE 1.4.2 is NOT the latest version of SODE so, GSX is correct saying your 1.4.2 is outdated, because it is.
The latest version of SODE is 1.5.0, and it's included with the new GSX installer so, if you do as the installer says, and Uninstall SODE 1.4.2, it will install the 1.5.0 version without having to download it separately.
The GSX installer checks the SODE version in the registry so, if you have Uninstalled it properly, the registry should have been cleared so, if you are still seeing that message, it seems something went wrong Uninstalling SODE, so the old registry key for 1.4.2 is still there.
The SODE registry keys might be located here:
HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\12bPilot\SimObject Display Engine\Version
HKEY_CURRENT_USER\SOFTWARE\12bPilot\SimObject Display Engine\Version
Be sure that both of them are empty, after Uninstalling the existing SODE. If not, remove the Version key.