5. Shelby GT500
Over the years the Mustang had some performance versions like the GT with the 289 HiPo V8 engine or Shelby GT 350 in 1965. However, the first true performance Mustang with big block engine and respectable 0 to 60 mph times was the 1967 Shelby GT 500. Bigger and more powerful than before, the 1967 GT 500 featured a new design.
Also, Ford modified the front and rear end and added a big 427 V8 engine delivering 335 HP and 420 lb-ft of torque. But in those days, Ford was notorious for underrating the power output of their engines, so 335 HP sounded too little for the big 427. So some Mustang enthusiasts claim the real power was closer to the 400 HP range. And the performance figures backed that claim.