The next level of engine ID is the engine tag. The engine tag includes information on engine calibration, date of manufacture, and assembly plant. Ford’s method of identifying engines varied in style and location. Some of them are stickers, others ink.
It is possible that they can be switched or fade over time, so the identification of an engine can become difficult. Here are some of the ways to identify an engine.
https://www.diyford.com/ford-modular-engine-identification-guide/
MG ZT info mods and maintenance 