So I'm still rocking the i7 920 that has served me well since 09. I've had it overclocked to 4.0GHZ with a third party after market cooler (Xigmatek Dark knight). I've just purchased a GTX 1070 and I'm hoping to extend the life of my CPU just a bit longer by switching over to water cooling. Hoping to hit 4.2GHZ. What water cooling kit do you guys recommend? I see the Corsair H60 is 49.99 after mail in rebate at newegg.

You can probably do 4.2 with the xigmatek, just keep the load temps below 85c and the voltage below 1.45V and it'll be fine.
 
If your set on an AIO all I can suggest is to get a one with a 240mm rad at the minimum. An H60 or similar will perform about the same as your current cooler. 

I am running an i7 970 at 4.2ghz / 1.32v. I have it under an EK Predator 240 and temps never exceed 70C. I was hitting 80C with my old Megahalem. The Swiftech AIO's are great too but I found EK's AIO to be cleaner and less flashy looking. Also, with the recent price drop I can't find a reason not to go with the EK kits. 4.2ghz should be breeze with a 920 under water. Your current cooler should be able to handle 4.2ghz as well. A Corsair H60 will likely perform worse than your current cooler. Maybe a bit better if you use some strong fans in push/pull but that will be noisy. 
 
I am currently running a 1080 Hybrid. LONG LIVE X58!!!

i just bought a master liquid pro from cooler master for my sandy bridge 2600k and 10 to 20 degrees off of my temps. in the heat of summer. i was using an evga superclocked cpu cooler that i won like 5 years ago or so. it was collecting dust that would not come off so i replaced with that http://www.newegg.com/Product/Product.aspx?Item=N82E16835103209&cm_re=coolermaster-_-35-103-209-_-Product  with both coolers i was able to over clock 4.5ghz and i still use the sandybridge and z68 sli.