Cool Mark, but I will say that 6 hours is a very good time. The best time is usually around 5:20. So I would say to take it as it comes. It will be much more humid than you are used to in Cali and that can wear you down. Just remember that Marion is the halfway point for effort. The lead pack will do the 74 miles to Marion in about 3:20.
Try to get to the start area no later than 5:45 to get a parking place in the civic center lot.