I'm afraid I haven't played GTA IV on PC and I haven't tried an i5 with this card. I actually use a FX-8320 that runs at 3.5 GHz. What I can say is that I'v played some of the most demanding games for PC and my 770 4GB has pwned all of them. Like, for instance, I played Watch Dogs on ultra, MSAAx4 (SMAA sometimes depending on how many fps I want) with the E3 mods installed on it and I get an average of high 30's-50 fps. I'm guessing you'll be able to play Watch Dogs at a higher fps than me since your CPU is a little better than mine I think.
So if I can run Watch Dogs with my set-up than you can most assuredly run GTA IV on your PC at ultra and 45 fps easily. You'll probably run it at 60 fps or much higher. I really doubt it'll drop under 45 fps and it does it'll because of your Hard Drive was loading or something weird like that lol.
Here's a video showing someone playing GTA IV on ultra at 1080p with a GTX 770 (he's using the 2GB version) and an i5-4670k:https://www.youtube.com/watch?v=-xTFRfBW97k
You'll be able to run it easily