being the mathed nerd I am, I'd blast an old 3 main downdraft with a procharger and go with it... all 1781cc of it.
sustainability goes with the rally more than the race.
funny enough, the race described at wikipedia is attempting to mimick the movie "cannonball run", and the high spirited fun that goes with it. the original had a crazy ea81 hatchback.. to this day, not one engine groupy would know why...unless they know engines. As stupid as the movie was portraying rich people and thier cars, the little sube added some casual hidden genius.
I like the race, glad it is afforded. Who else would do it? they ought to make it more news worthy for like a spectator...