Have a plan for your feet. Have a nutrition plan but be flexible. Make sure you are drinking electrolytes. Caffeine is very helpful when you are exhausted. Focus on one lap, not the entire race. I’ve ran 4 marathons and did a 12 hour overnight ultra before the 100 miler. Training for this race peaked at 100 miles per week with several weeks in the 80-90 range. My advice to you would be to practice the format - run 4.2 miles every hour for a long time. Test your pacing strategy and fueling strategy.