It's been a while since I did a Cannonball, mostly because I struggle for ideas. Was struggling this year as well, but I think I finally have it:
Plain brown wrapper, high output engine, no one would look at it twice and anyone that did would assume it to be an unmarked. I think I have a Missing Link '71 body to turn it into a proper Gator McKlusky car, but have to do some digging in the stash to confirm.