There's a lot more to it than you think, your better off selling both cars and buying a used gt or a new one.
I just swapped my 4.0l mustang to a 5.4l. You have to remember, motor mounts, trans mounts, wiring harness, transmission, shifter, driveshaft, misc bolts nuts and if you want a/c and all the other bits and pices. I'm not saying it's not rewarding doing it, because it really is. There's a whole lot to it. You need to start with not just a doner car but at least a similar car to get the swap from...such as mustang gt to mustang lx.
Pcm, ecu fuel pump...gosh the list goes on and on. Just get a gt. I hate being the nay sayer but I'm just giving you wise advice.
here's a video of the fun you can have if you end up blowing 8k on a nice swap and your time.