Has anyone put a 2011 v6 mustang engine into a 60s mustang?
If you're asking "how hard" it is to do the swap, and "how much" it costs, then you're already getting into a nearly impossible project. A project like this is a "cost-is-no-option" venture.
Any modern fuel injected engine is not going to play well with a 60s-era Mustang, ESPECIALLY the 2011 model. The new Mustang engine is entirely dependent on computerized electronics, throttle, and transmission parts. You'll not be able to keep the car looking anywhere near "stock", as you'll literally have to rip EVERYTHING out and start with a bare car frame.
You might be doing better buying a new carbureted crate motor. That will be the closest you can get to a "swap" solution.