Seems you may have entered the Twilight Zone.
The frame is what you should use to date your A.
The engine if not the same can be anything/any year. During the life of a 90 year old Model A, a lot of things could have happened. Not uncommon for there to be Frankenstein cars. People were a lot more resourceful, lots of used parts used on Backyard and 3rd party mechanic repairs to the point were you can have all kinds of parts/aftermarket parts/etc, even from different years mixed in. This is why restoring to original A can be so difficult, and why it is rare to find an original/untouched car, or at least a car with all original or period correct parts.