In GTA V installation directory there is a file called GameBackups.rph. I used 7zip to open it, but it should be possible to rename it to, say, GameBackups.zip instead. Then you can open it with WinZip or WinRAR (or perhaps even windows).
Inside this is another archive, named after the version it is, 1.0.617.1,1.0.505.2. Open that and inside there you should find three files, GTA5.exe, GTAVLauncher.exe and update.rpf. Place the two EXEs go into the installation directory of GTA V, the update.rpf goes into the Update folder found there.
Hope this helps.