'69 AMT bucket is wider and shorter, last time I pulled an annual off the shelf. Curiously, the chassis is a 1-pc that is a decent fit in the Mach 1 showcar / Iron Horse.
'69 MPC - the very common '69 kit - is underscale by a few percent. Revell is really 1/24 despite the 1/25 claim on the box, would require much slicing dicing to fit.
I'm strictly guessing here, but I will wager the '70 AMT Blue Crescent shell became the '71-3 - some of the contours align, but there is zero detail of any king correct for a '70.