This generation of Mustang had a physical refresh. The refresh saw Fords designers make the Mustang look more imposing, more "racey", and much bigger!
The Engine power was also increased again in the Shelby ranges.
The GT500 set the bar for performance, going 0 to 60 in 6.2 seconds. It is maybe most recognisable to the newer generation as a car named "Eleanor" from the film Gone in 60 seconds.
In the redesign, Ford made the Mustang bigger in all directions.
It kept the same basic appearance, but the expansion allowed for better handling and the engine bay could fit larger engines.