Great link Jay, thanks. Sometimes Google gives too much
So I just checked out the difference btween them and here they are...
The 73 has one inch longer wheelbase, is less than 6 inches wider, about a foot longer (mostly in overhang) and is actually shorter than a 65.
The 73 has a one inch longer wheelbase, is 3 inches wider, six inches longer, and also shorter than a 70.
So there's as much difference (or more) between the 65 and 70 than there is between the 73 and 70, but folks don't call the 69-70 "tankstangs".
I'm not saying they aren't bigger, duh, but much of what makes them bigger has more to to with aesthetics and design/lines than measuring tapes. Before I knew these details I'd have said they were two feet longer, a thousand pounds heavier and a foot wider.
EDIT: Not calling all of his facts into question but there's a number of erroneous statements on the 1967 page. Not just factiods but the weight measurements too. There's no way a 67 Mustang ever weighed 3,910 pounds, not with every option imaginable, a FE with AC and a convertible...no way. Unless perhaps William 'Fridge' Perry was driving it...nope still not.