Putting a 4.6 into a 2011 or newer is kinda stupid. If you're gonna go backwards like that, do what I did, and go WAY back - put a Windsor in the car.
But since you're starting out with a v6 you'll need another $10K in suspension mods, new rear axle, brakes, etc.
Actually, the rear end in a 2012 v6 uses 31-spline axles, and the rear brakes are the same as the GT. As for the front brakes, upgrading to GT brakes (bigger rotor and maybe different calipers) is pretty cheap, but if his wheels are big enough (he needs at least 18's for this), he could just go ahead and get some 4-piston brembos (and of course, the appropriate rotors to go with them). So, costs to upgrade would be as little as $400-700 (rotors and calipers), depending on if using new parts, too. Struts/shocks shouldn't be an issue, but he should plan on upgrading if he's running OEM parts. All in, his suspension/brake upgrade shouldn't cost more than $1800.
The engine is the cheap part. The v6 running gear is not capable of handling that much power safely and will be a death trap.
If I'm not mistaken, the transmission is the same for the v6 and v8, but it is something he should research.
Honestly it would be cheaper to go buy a new car.
This. If you want a V8, get a 2011+ GT (older GT's can be had for less than $15k). It's faster and cheaper than doing a motor swap of any description. When the topic of a motor swap comes up, this is my standard advice (having done it myself).
If you insist on doing it, research, research, and more research - consider the ENTIRE car, meaning every system and sub-system, such as cooling, electrical, driver train, fuel delivery, etc. Find out how much everything is going to cost, and to be brutally honest, there's no such thing as a "budget" when you start doing a motor swap. Once you figure out how much all the parts will cost, add at least 10-15% of that number for after-though "upgrades", "incidentals" and "no-see-ums", and start saving money to buy those parts.
After you've saved enough money, gather ALL of the parts you'll need before removing the first bolt (I cannot stress this enough).
If you still wanna do all this, I wish you luck in your endeavor, but then again, just buying a V8 car is faster and cheaper. Did I already mention that?