Jim is right...we have to go by the Registry, but remember it is now almost 7 years old and a lot of history and data has been uncovered since it was last printed. SAAC's records are the most accurate source.
Here is an interesting bit of data...
Excerpts from the 1966 Cobra brochure and then the 1967 one.
The 1966 sheet calls out the 427, while the 1967 calls out the 428. It is widely believed that the cut-in of the 428's came at about the model year change, coincident with the switch to round taillights.
A new program manager at SAI facilitated the switch back to 427's for the last 60 or so cars, until production was ended.
1966 version:
1967 version:
