Quite a few months ago I was driving when my engine started knocking in my 2000 Grand Prix GTP. I was forced to pull over to the side of the road as the engine began to lose power. I tried starting it again and nothing, so I called AAA and they had it towed to a mechanics shop here in town. After inspecting the engine the mechanic let me know that the engine was "dead" (I don't think he used that exact word)....so I would need to replace it. I told him to do it, and after a week or so I went back to go pick it up. When I went to pick it up he let me know he couldn't get another engine from my generation so he went with the next one up (so it should of a been a Supercharged 3800 Series III [L32], but I didn't know that at the time) and that all he had to do was modify the oil pan. Within a couple of weeks that engine ended up failing on me as well, same thing happened, started knocking and then lost power. So I took it back and he replaced the engine once again, I asked him what engine he put in it this time around and all he said was, "The same one." I believed him at the point so I took the car and went on with my life. Well now that I'm doing some more research on the Grand Prix I'm realizing that the first time he put the "new" engine in it that the engine cover actually said "Series II" and even after putting the second "new" engine in it that it still has a series II engine cover on it. So either he didn't put a Series III engine in it or he just put on my original Series II engine cover on the Series III. I don't know how to tell the difference between the two with the exception of the engine cover, which doesn't help in my situation. Is there a visual distinction between the two motors? Or where can I find an engine identification code?
Thanks in advance for any help/advice.