L 78 dated carb

[Mr70]

As the engine ass’bly date is the date that all pieces on the engine must precede.

Not necessarily true,the Carburetor was put on the engine AFTER Tonawanda stamped their assembly date on it,which documented when it became a single running unit.
They used a propane device to fire the engine,in place of a carburetor as it didn't have a fuel line/gas tank attached to it yet,and also couldn't,due to that being a fire hazard during shipment.
So they had to be shipped to their destined car manufacturer "dry".
So technically,you could have an engine with a carburetor date PROceeding your Tonawanda assembly date.