Look at the specs from the first generation mustang to the 71, 72 and 73.
Different wheel base, different length, different width and different weight.
Vastly different car. I don’t know how anybody could consider a 71 model as a first generation.
Either hate or love the mustang II, but it must be admitted that it was truer to the original mustang pony car then those big Torino type mustangs.
IMO, 63-73 had the same basic, original Mustang look, although of course the 69-73s were longer.