There are some senior AACA judges on this forum who can provide feedback. I have run seven cars through Grand National, so I can try to respond. The car will be judged to be as it was delivered from the dealership to the first owner. Any dealer modifications, however, must be documented as having been offered by the dealer. For example - my 69 Yenko Camaro had Atlas wheels and traction bars - I did not receive any deductions for those additions because I had Yenko literature that indicated them as optional dealership additions.
You will need your bumper jack. Also, depending on the level of expertise of the judges, you may need correct stickers in place. The most common major deductions on first junior judging are for radial tires, halogen headlights, and incorrect batteries (correct battery topper will receive most of the points).
In general, AACA judging is a great experience - you'll meet some really fine People for sure.