Mid year 273 in 64 Darts?

If the 273 had been available at the beginning of the 64 model year (i.e., in September or so), Hot Rod Magazine's "exclusive" December 1963 article about the new 273 motor would have been seriously out of date.

I sure can't claim to be the final word on the subject, but everything I've seen supports the Slant 6 News' claim that production of the motor began in December followed by January availability of the
motor in actual cars. Where Jack Poehler (Slant 6 News editor) would have gotten that information from, I have no idea, and he is no longer around to tell us.

Obviously, 273 blocks used in those December 1963 built motors (and probably many built in 64) would have been cast earlier in 63.