elantra engine ground connection

I purchased a 200 amp alternator for my 04' hyundai elantra and I'm replacing all the wiring with 2 ga. wire.  I traced the ground cable from the battery but it goes somewhere hidden behind the engine.  I can't feel how far it goes, but I do need to replace it since the factory wire is like an 8 or 6 gauge wire.  Does anyone have experience with this car or any suggestions on how to trace it.

Happy thanksgiving.

I took the air filter off and I was able to see the engine bolt that it is connected to.  I have a dual battery set up with one in the trunk and the stock in the front.  I didn't find a wire that leads from the engine to the frame, but I wired the two battery grounds directly to each other and to the engine ground.  I think that should be good enough.

Why does the positive run to the top of the engine?  Is the starter up there?