GTX 270 has TDP of about 219watts @ stock speeds (x2 for your setup)
i5 760 95 watts @ stock speeds
You are looking at around 533 watts for this loop. Depending on your budget and how and where you want to mount radiators (and which rads you choose) you will be pushing it close with a single 3x120 rad if you keep everything at stock speeds. It would work, but you wouldn't really have much room for overclocking unless you added another 120 or 140 rad.
What is your budget? Have you read the watercooling sticky (linked in my sig below)
Right now I'm thinking of using a Swiftech MCP655 pump, and two XSPC RX360, which I hope to place outside of the case as I don't think they will fit. Not sure about everything else though. Seems with this I will go over $600.