Before we begin navigate to your game directory and copy "GTAVLauncher" to a folder on your desktop. We'll need this later.
Download and Install RagePluginHook if you don't already have it.
Launch Rage and open the settings.
In the settings you want to navigate to "Game Settings" and open the "Revert Game Version" Dropdown.
Check Version 1.0.1604.0 is listed there and then select the option to downgrade (Might be labeled "Upgrade")
Once this is complete Exit ragepluginhook and press windows
Search for "RegEdit" and hit enter
Now navigate into the following location within the directory of registry editor.
"HKEY_LOCAL_MACHINE" > "SOFTWARE" > "Wow6432Node"
When there look for "Rockstar Games"
Right click and Add a new key <Click this text to see what I mean by this>
Name the key "Grand Theft Auto V" and enter that new directory
In here add a new string named "InstallFolder"
When you have named it right click and modify the string value. In here you want to get your game directory's path such as "C:\Program Files (x86)\Steam\steamapps\common\Grand Theft Auto V" (The default Steam location if the steam location hasn't been modified).
Copy the directory location and paste it into the modifier. Save and exit registry editor.
At this point you can now properly install GTA V Launcher but will get stuck in a loop. To fix this go to the area where you stored your previous "GTAVLaucher" and copy that. Paste it into the GTA V directory and Replace the file when prompted.
Upon launching VIA Steam or Rage you will no longer be prompted with any Errors or the infinite Launcher Install loop.
(SIDE NOTE: If you use steam, ensure to set the update settings to Ask when I launch the game to stop Steam from auto updating like it always does as updates always break mods.)
Hope this tutorial helped you!
~SnickeredTV