The speed of a Mustang GT depends on the model year. Performance specs change from year to year. However, a general range for 0-60 mph acceleration for modern Mustang GTs (roughly the last 10-15 years) is
around 4-4.5 seconds. Top speed is typically electronically limited, but generally falls within the
150-160 mph range.
To get the precise figures, you'd need to specify the exact year and model of the Mustang GT you're interested in.
