I am in the same boat here. I have the steam version.
My method(used to work fine) was to back up a version of GTAV on a flash drive. Once backed up and mods removed from game folder. I update my game through steam. Once that was finished, I would open the game directory and delete the updated GTAV. After that I would copy and past the older working modded GTAV into the steam game directory. Then once that was done, I launched my game and it worked fine.
Unfortunately I did this method today and the game would only load if I removed my "mods" folder. Scripts and .asi's work fine. When the "mods" folder is put back, I get an infinite loading screen when I load into story mode. What would be wrong with my "mods" folder since I am using a pre "summer update" game anyway? I don't get it, this worked for me before.
I just got this game to be smooth and stable again but of course greedstar released an update that everyone will be bored with by the end of next week.