I love this car, even though it drives like a truck, isn't fast, doesn't get all that good fuel economy, and is difficult to find parts for.
My convertible has a 200ci 6 cylinder under the hood and isn't what I would call quick. 0-60 takes around 11 seconds and top speed is around 100mph, that is assuming you are brave enough to take it up that high. You may say to yourself, "Well, I'll buy one, then beef it up." Good Luck! There is an Australian intake that will add 3 Weber side draft carbs. That intake is around $800, and you should have a 250ci head and bigger headers. All in all, a 5 lug/V8 swap would be cheaper/more practical.
I researched swapping in a 5 lug front disk conversion. That will total around $2500-3500 (including rims and tires). That's not including the engine/labor.
I just turned 17 years old and decided to restore the interior. Originally, the dash was made of brushed aluminum. My father always had the top down when he had the car, and eventually it discolored and he sprayed it flat black. I bought just about every part in the interior (except the seat covers/foam, and carpet). Including 4 Diamond speakers, the total was around $2500, which is a lot. Mind you, this is not including labor, My brother and I installed everything ourselves.
The Mustang was "a metal metaphor for America". It will always be one of the coolest American Muscle cars and will always look good, which is one of its best features.
On the whole, these cars aren't the cheapest, fastest, or nicest cars in the world, but they have plenty of character and if you care about your Mustang, it will show. You will likely fall in love with your mustang, especially if you buy a project and build it yourself. This is probably one of the cheapest muscle cars to run/own (with the 6).
I recommend buying a Mustang if you are looking for a nice clean get around car, not a commuter. I also recommend you try a car out before buying it, Mustangs are not easy cars to live with, especially every day, make sure you are committed to driving and enjoying the car, not just using it to get from a to b.