Not sure what exactly you need the vehicle to do for you (track, drag strip, windy roads, bragging rights?), but for longevity avoid the Mustang GT.  Those two cars are in different leagues/classes and accomplish different missions.

Unfortunately, the terms "fast car and "long time" rarely go together.  People who want fast cars drive them irresponsibly and either break them or wear them out prematurely. 

When it comes to fast or performance cars, a wise mechanic once told me:  “Fast, cheap, reliable:   Pick any 2 of the 3, but you can’t have all 3”

Have you looked at a used Lexus RC F (suggested by another member above), a RC350 Fsport, or a Honda Civic Type R?  They are not giving any of these away, of course.

Get a Lexus RC F 

The mustang can last 200,000 miles if maintained properly and drive properly. But who would buy a mustang and drive like a 80 year old grandma?

for what you're going to spend on one of those, why not look for an older muscle car?

there's plenty to choose from and if you drive them REAL fast, you won't have to worry about reliability. just get lots of hospital insurance!

Those two cars don't compare.  The toyota would be more reliable. 

how fast?

been wanting a v8 lexus, supposed to git 155 mph lol