Not exactly sure what you mean, but the conversation was only about 71-73s. Nobody ever said the 69-70s were particularly small...they weren't. But the fact is that that 71-73s were bigger in nearly every dimension than any Mustang that had come before. It grew in one direction, the market moved in another.
The typical trend in Detroit then was that all cars would naturally grow as they "matured". The Mustang was no different in that respect.
It is well known that Iacocca did not agree with that thinking. He hated the HF-II demanded "enlargement' of the 67-68s..he called them a "fat pig"! That is why he rallied so hard for the smaller "Mustang II". That car was definitelty his baby, maybe even more of his influence in it than the original 65'.
He had been lobbying HF-II for several years about "downsizing" the entire Ford line, well aware of the coming onslaught of small foreign imports and the effect they were going to have. He was very prescient in that particular regard.
HF-II would have none of it. He felt if there was to be a smaller car, it would be a new model, not a smaller version of an existing model. The Maverick in '69 was Iacocca's first half-hearted attempt to recapture what he saw as the Mustang's true personality...a small economical sporty car...not the fire-breathing beheamoth it had become. It was very succesfull.
The Thunderbid had become fat and lazy by '72, a hulking psuedo-Lincoln and light-years away from everything the "Thunderbird' had originally been designed as. Its sales peaked at 92,500 in 1960 and had plummeted to 36,000 by 1971.
In '72 it began its 5-year run as a virtual clone of the Lincoln Mark series and sales styed low.
Iacocca pushed for downsizing, Henry Ford II refused saying "America likes big cars". Somehow, Iacocca put the plans in motion for a new, smaller & lighter,and importantly: cheaper Thunderbird for 1977 without HF II really understanding what was happening. (That doesn't make sense to me...)
The new smaller 1977 Thunderbird was a SMASH hit! it sold 320,000 units in ONE YEAR! That is more than a 700% increase over the previous year.
And it is more than 400% higher than any single previous year of Thunderbird.
That generation ran for 3 years: 77-79. production for that 3-year run was over 955,000 units. That is more sales than the previous 16 YEARS combined!
But...the success of the car was Iacocca's downfall. He was celebrated as the mover and shaker at Ford...and HF II did not like anyone having the spotlight. It was shocking at the time, but on the ev of the greatest sales sucess and turnaround of any nameplate in history, HF II fired iacocca, the man responsible for making it happen.
GM downsized thier entire line in 77...and slaughtered Ford in the process until finally HF II gave in and allowed the downsizing, but it took until 1980 to begin, and until 83 or so for it to take full effect of the entire line. Millions of sales were lost to GM.
So, whats the point?
The Mustang did indeed grow every generation, just like every car did back then. The 71-73s would probably would not be so poorly remembered if the market hadn't taken such a swift and dramatic turn in a new direction.
Camaro and Firebird sales had fallen off so much that they were both cancelled in 1971. If not for a couple of very vocal and aggresive GM insiders who lobbied endlessly to keep them going, they would surely have ended there. Herb Adams was one...he is one of the great auto engineers that doesn't get much mention. John Schinella was head of one of GMs design divison...he loved those cars. And of course there is Bill Mitchell, famed Corvette guy...maybe second only to Zora himself.
History likes to paint Ford Motor as a doofus company for selling the "wrong" Mustang in 71-73. But there is no way they could have forseen any of this in 67-68, when the car was being designed and planned. The design of the car is a logical and expected result of what would have naturally been predicted back in 68. They just designed what they thought peoiple were going to want.
And they all got caught: Chrysler dumped its Cuda/ Challenger twins after dismal sales form 71-74, the Camaro-Bird barely survived, and everything else died: No more Javelins or AMXs,no more small-ish Chevelles, Skylarks, Regals or Cutlasses.
The only pony car that really survived unscathed was the only pony car to begin with: the Mustang.
Personally I don't think of the 71-73s as "too big", not by a long shot. I think of them as "just right". But...I do think of previous generations of Mustang as too small! Cramped, poor handling and rough-riding, thats my own opinion of 65-70 Mustangs, as compared to our 71-73s.
But, I am also a pretty big guy: 6'3", about 280 lbs. I was well over 230 in my youth when I first got the car, so I need a bigger Mustang!
Its funny, most people remember the last Torinos as "huge" cars, but mine (a 74 and a 75) actually seem smaller than I remember every time i get in it and drive it. To me, it is just the right size (basically, exactly the same car as the 77-79 Tbird, 72-75 Montego, 74-79 Cougar, 74-76 Elite) That chassis got quite a workout in the Ford line!