Yep I do. It's a bit of a hassle to get there, because you have to jump through some hoops (let me know if you can't find the guide via google), but modders say that 184.108.40.206. prevents some of the visual effects from ENB, and I've personally found the ENBs for 1040 to be more visually pleasing too, so I think there's something to it. If you look at some of the other threads and on different sites, most will tell you not to even mess with 1070, but I think that's a little overkill. I liked a couple ebbs for 1070.
Now performance is a different issue. I don't have a SLI set up, but have heard SLI doesn't work for GTA 4 (lame). The issue (I read) is the game's code, which was poorly designed and inefficient. So the game is CPU intensive, and may even run better from one of your 680s.
I could be wrong but I don't think there's much performance difference between the two patches, but as you start downloaded different mods (guns, cars, sounds and many ENBs), your'll notice the authors notes will say 1040 only or it will work in 1070, but not as well (I.e. graphics aren't as good). I made the move early on, but kept a clean version of 1070 installed on my data drive (and a 1040 copy as well), as there are some pretty good mods for 1070, just way more for 1040, and ere are visually better, IMO. Like you I overclocked both CPU and GPU, and still max out around 35 fps, and it drops sometimes into mid 20s. I've found that water reflections crush performance and don't add a ton visually, so I turn that down a bit, and cars to roughly 40 percent. I've also found, and could be my imagination, that running from SSD boosted performance a little. What you can do is find a ENB you like, and tweak the settings a little...like car reflections, for example, which hit performance hard. If you nudge the settings down, sometimes you can gain a few fps. The biggest hit by far is the the global shadow detail... Forgetting the name but its shift f11 I think, or can turn off in enbseries.ini. That kills performance and doesn't add a ton IMO...especially when your driving around at 100 mph. I can be more helpful when I have it up in front of me.
Keep in mind if you do flip over to 1040, you'll need the versions of script hook, xliveless, etc for 1070. I can put those up for you to download somewhere when I get back...problem is that sometimes on the boards people mislabel them, to add to frustration. Like I said, modding GTA 4 can be challenging, and sometimes things work right off the bat and other times you spend hours f'ing around and sometimes mods work with just xliveless and sometimes dsound...can be frustrating. But once you dial in a few set ups (I have one set up for higher fps, when I get sick of playing at 30), its worth it.
And you won't need steam up for the 1040 patch either to launch the game. I just make shortcuts of the launchgta.exe files, and its good to go. Makes it easy to back up the set up you like and revert if anything goes south.
Hopefully gta5 is coded better to take better advantage of high performance hardware. Seriously, if your set up gets crushed, it says something. Two 680 4gbs in SLI and 20-30fps is ridiculous.