You will want the VIN number, which is at the back of the engine, above the transmission. It is just below where the head meets.
You can see it if you remove the air intake hose and get creative with a flash light and mirror... the coolant hose/pipes are a bit in the way, but nothing making it impossible.
Here is a rough idea of the location:
Disregard the B, that's the balance shaft check hole, I have no idea why they marked that. There is also a serial number on the block below the #1 exhaust port, however it is of no use to us without the VIN unfortunately so we have to have that regardless.
Remember the VIN should be engraved, not on a plate even though it looks that way in the picture, so you may have to take a soaked rag and scrub the block a bit to get a good read. If you can't read all of it that is OK, just make sure the first digit is a 4
and the 10th digit is 2, 3 ,4 or 5.