Around 1971, my GF's (later wife) younger sister was attending Ohio U in Athens OH. She needed a ride back to school so my GF and I took her using their 66 Mustang coupe. We did the round trip in one day, probably 3-1/2 hrs each way with me doing all the driving on highways winding through the hills in southern Ohio. 289-2 and clunky 3 speed manual on the floor. I didn't drive fast at all and doubt that I ever floored it.
My everyday car was a 1967 Barracuda FB, 273 Commando 4 speed but not a Formula S, so 10" drums and no sway bar.
I was surprised at the difference in handling. What I remember is the Mustang had a wallowy front end and the tail was low. Why is it most of the vintage Mustangs are tail draggers?
Anyway, I thought my cuda was much more stable and predictable. I scored a lot of points with my future FIL when I helped him change the heater core in it. They had a new house built and moved in early 1972. That thing sat around for a few yrs befire he eventually junked it.