How do u know engine model??????????
How do u know engine model?????????? 
is there number or something else?? 
If you are reffering to LSx engines the easiest way it to look on the head. It will be stamped on the driver side rear and passenger side front of the head right above the exhaust port. it will say 241, 853, 243 or something. This will help determine the year and engine type. You can also get the casting number off of the rear of the block driver side. Also behind the flywheel there will be a 5.7, 6.0L etc stamped on it.
241 heads were used on fbodys from late 2000 to early 2001, on vettes from 2000-2004, and im unsure of what year GTOs but the first few years i know they had LS1s which im assuming had 241 heads. The later years would he LS2s which would have 317 on their heads i beilive. I'm not really sure how you would tell which model it was from. You could look at the accessories i suppose. Why does it matter?
