I've found that 250-300kcal/hr is pretty good for the first 3-4 hours. I tend to increase after that. Drink as much as you need whenever you need, but absolutely plan your food stops. I try to take in food every hour (if there's a good amount of climbing) or twenty miles (if it's relatively flat.) The first two food stops are often tough, because I'm usually not hungry yet-- but if you skip a stop, you can never make it back up, and you'll turn the last 20 (or more) miles into misery. During a double metric, you can eat most anything you want after mile 80 or so, I usually go for a full meal around then as 3/4 of the ride is done and I should be mostly fueled by then-- enough to finish the ride, so the eating then is so that I don't try to devour everything in sight when the ride is over.
Clif Bars or fig bars are good for the first two or three stops. I start looking for more straight carbs (sugar) after that. I did 140 miles two weeks ago, and my food timing/intake worked out really well. Mile 80 was an Icee and an order of french fries, so what you eat matters a whole lot less than when you eat it. Mile 125 I ate two Milky Way bars. At any mileage past 100, anything ice cream is a revelation. A cone from the RiteAid, a Drumstick from a convenience store, a scoop of gelato from a place on the boardwalk. It's magical. Ice cream is sugar + fat + salt, and we love all of those things.
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