Are you sure of that Daniel?
Some engines were built and sat on a rack for weeks to months before being installed in a car. So in this case for alternators that were installed during engine dressing, the date stamped may very well come before or after the engine build date depending on the volume and popularity of parts consumed on the assembly line.
In the case of my 2 '67's with originl electrical parts the LOS built car has the optional alternator so it sat for a while and was built before the engine assembly date before being installed.
The NOR car used the standard 37A unit so the build date was more recent relative to the cowl assembly date but after the engine build date.
LOS- Engine date - T0214 - Cowl date - 4B (UOIT lists 4/13/67 specifically)- Alternator date 7A30 (optional 1100696 - 42A) - Voltage regulator date 7C
NOR - Engine date T0308 - Cowl date - 5B - Alternator date 7E4 (standard 1100693 -37A) - voltge regulator date - 7E
Or did you mean engine build = engine dressing?