Eating and drinking enough will be a big challenge. You will be burning a lot of calories. Long hours of Zone 2 in your training will build up your ability to burn fat while riding. You will need this, but it won't get you to the end. Eating will be essential.
On your long rides try different foods and drinks and see which ones agree with you and which ones don't. It sucks to find out that your body rejects the food you brought when you are 80 miles into a ride.