AAX86

I can't remember what year the owner said the engine was when I bought the car. I want to say either 1990 or 1993 but I'm not sure. Where would I find a serial number on the engine or some other means of identifying the year the engine was made?
I have pictures if some of you are familiar enough with 5.0's to tell the year. I'm mostly worried about whether it's pre-1987 or not for when I have to buy new parts


Btw sorry if this isn't considered a tech question.. I do that every time.