Depends on the engine - six, small block V8, FE?
Since you mention Dearborn, I'll assume you are talking FEs. All FEs were assembled at the Dearborn (Rouge) Engine Plant (DEP). From there they were transported across the site to the Dearborn Assembly Plant (DAP) and all other vehicle assembly plants that used FE's not just Metuchen and Milpitas (San Jose).
Remember that FEs were used in other car lines, and trucks also, so the batch concept is not an accurate mental model for engine
assembly. Meeting a retired Ford engineer tonight, in fact. He was the "390 engineer" in 1967 and 1968. I'll ask.
If you look at parts (blocks, heads, etc.) the batch process has more applicability.
Are you asking about individual casting and stamping date variability, or engine assembly date variability?