My father and I restored a 64.5 Mustang. It was a V8 (think it was a 287 c.i or 289 c.i). Unusual thing about it was the factory bench seats and a factory add-on a/c. It was an automatic with a floor shift.
Those under-dash A/C units were the only type available in the Mustang through '66. Very capable, too - I had one that would make frost form on the chrome plastic vents.