thats a great deal. My brother just paid 44k for an 11 with 4k miles.
What are your plans for the car. If your going to leave it stock I would say no. It's kind of dissapointing stock. If your going to do bolt ons or other mods you should definately do the swap. These things are animals and will add power for cheaper then a 5.0 could only dream about.
Well if you look at the road kill section, it seems like the 5.0s are the cars to have. I saw a thread in the 11-14 mustang section that outlined the fact that the 5.0 is a better car than the gt500 period. I would stick with the 5.0 if I were you, i am actually contemplating getting rid of my 11 gt500 for a 14 5.0. I spent thousands of dollars on getting my gt500 to take a C6z and it seems like most 5.0 guys only need simple bolt ons.
I traded a 11 5.0 for my 12 GT500. Happy I did but damn I miss revving it to 7000 RPMs