Just a little info from Dan at American Muscle Via the facebook page. Based on the number of cars registered to go, he is saying for people to start showing up as early before 7am Saturday morning. They are planning on starting to park cars by 8am (or when the line starts becoming crazy long). They are anticipating thousands and thousands of cars and spectators and want to have everyone parked as early as they can to get the show started!
Also, if your pre-registered pass has not shown up yet, print out your confirmation email or order from the website and that will allow you access in the show if you paid for it and are still waiting on the pass.
If you have any questions, AM has a thread going on their facebook page with staff answering as many questions as they can.