My dad bought a 65 Mustang with the 6 cylinder and 3 speed manual gearbox. It was a pretty fun car. It only had 120hp but that was pretty average for the era. Most cars back then were very slow. Any Japanese econo-sedan today is faster and handles much better.
Then in 1980 my Dad bought another Mustang with the 4 cylinder and 4 speed box. What a hunk of junk. Terrible car. Everything started going south at the 60K mile mark. The 4 cylinder was so bad that the 6 cylinder version got better mileage. You had to floor the 4 cylinder all the time to get it to move. Lol.
Mustang II was a flop........................