GP 18 is just to the drivers side of the block.  Look where the head
attaches to the block on the top of the engine.  There is a thin coolant
pipe running parallel to the gasket, and you should see a brown wire with an
eyelet bolted to the head closer to the rear.

I used a bright trouble light to find mine, but I still had to remove the
intake runners to get enough access to clean the eyelet and bolt it down.

Good luck,

John Haddad