Is there a way of matching engine number to chassis number?

I sumbled upon this: http://www.jagrepair.com/images/TSB/X300/03.1EngineAJ16/03-1-04%20Poor%20Idle%20Quality.pdf
And wondered how the engines are numbered. The document is for the 1995 model year. I have a 1996 3.2l X300. Yet the engine number is LOWER than the ones mentioned in the document. Did the 4.0s have higher engine numbers? Or are they different on the US models? Or do I not have the original engine installed?