It's gonna be a long day....
Are you going to get to a destination or power sight see or ?
Take breaks every hour or so. Even if you have to pull off and just stretch your legs. Get a good night sleep the night before and try to eat right.
Have a water bottle available to stay hydrated.
That's all I have for now but there's tons more out there.
Stay hydrated. Start at the crack of dawn. At a reasonable pace figure 3 tanks of gas and you will be there. Listen to your body and rest when needed. Pushing it will only get you into trouble. When stopping to eat, do not get overly full. Be sure to take rain gear. Hit the road and enjoy you will be surprised how nice a long ride like this can be...............
Report back when you can...it makes us envious and sets our resolve. Remember stuff can loosen up so have some wrenches and listen with your rump and feet.
Sheep skin seat cover. Keeps your posterior cooler in the heat and warmer in the cold. And prevents butt burn when getting on a seat that's been sitting in the hot sun.
Many good suggestions already, looks like you're pretty well on your way. I've been lurking at this sight; Iron Butt Association and picked up a few tips.
My only addition to this would be "Know your route, turn by turn, before you go". Please, don't ask me how I know this. I can tell you, knowing your route before hand will save you hours.