I do not have any configeration files as this is a fresh install of GSX
Have you CHECKED if you have GSX configuration files ? If with "fresh install" you mean you reinstalled GSX, that wouldn't reset your configuration files, and rightly so, because it would be very wrong if uninstalling GSX would kill you all your configurations and preferences. Even reinstalling FSX won't remove any customization file in GSX.
The only case when you have a really "fresh" install of GSX, is when you reinstall Windows, or create a new user account.
The GSX configuration files for airplanes are in the following folder:
%APPDATA%\Virtuali\GSX
With each airplane having his own folder. These ARE being reset by the "Reset" option of the aircraft configuration menu. An airplane configuration file can ALSO be put into the main airplane folder under FSX\Simobjects\Airplanes\AIRPLANENAME, but in this case, it will NOT be removed by the "Reset" option, you must remove it manually, because that place is supposed to be used only by airplane developers (but of course nothing can stop you from putting a GSX.CFG file there...), so the "Reset" would "Reset" the airplane to the configuration provided by the airplane developer.
So, if you really want to be sure you don't have any configuration files, you should BOTH use the "Reset" option (which will remove the configuration under %APPDATA%) AND check in the FSX\Simobjects\Airplanes\AIRPLANENAME folder and manually remove any GSX.CFG you have there.
due to the fact that I could not even get the menu to come up.
If you used an older GSX installer you might have download a while ago, before those vehicles were added. The updated vehicles can be found in either the vehicle updates installers, OR in the current GSX Full installer.
But again, even if you have everything updated, a wrong configuration file made before support for high loaders was added, will still take precedence and will have to be removed.