More that than anything else, but there
are 2 primary shapes:
GJMalcyon's '61, from here:
https://letstalkguild.com/ltg/index.php?threads/f40-lovers-unite.195241/page-2 , in which a lot of pics are no longer available:
'56:
In late '63 F40 was replaced by F47, flat back 'hog body using same outline:
I know what you mean, though. I see a slight change in the "roundness" of the 'bouts when the shape was revised ca '72:
So it's like the upper bout used to appear a a bit "slope-shouldered" and with a "flat" bottom, morphing to something a bit more "square-shouldered" with a definitely rounder lower bout.
'75:
F47 was '64-'74 when F40 was revived until 'about '85 when Gruhn revamped the F-bodies.
That shape lasted with F47's through end of Corona ('04),
but F40 went on extended hiatus, except for the 45th Anniversary Valencia which used the original F40 "Valencia" outline:
When Tacoma revived the F40 they revived the earlier outline which carried through to NH, and body depths were slightly different IIRC.
I do not speak of the Oxnard F40, it is dead to me.