I'm an ultrarunner, who just took a year off to get both feet fixed surgically, and am back in the saddle. I've been paleo for several years now.
I would typically run between 18 and 35 miles on the weekend, of course through trails, then do short crossfit workouts during weeknights, with no additional miles those nights. I am starting that schedule again as I train for 2014's Beast Series/Lynchburg Series here in VA.
I trained with Amy Kubal (works for Robb Wolf) last year, and knowing my running/work/school schedule she still prescribed me a strict paleo diet. When I was running alot I had two cheat meals (not cheat days) a week, was allowed two ounces of 85% dark chocolate a week, and only 1-2 cups of coffee a day. I could only eat a larabar, 6-9 oz of sweet potato, or other paleo starch after a workout. I also could only have a protein shake after a long run. She was pretty strict but I felt amazing after doing her protocol while taking on the stress of ultrarunning.
She approved my mid-run snack, which at the time was either a larabar or my personal favorite, Paleo Plan's tapioca crepes stuffed with almond butter and sugar free jam. Again, I could only eat this during runs, but this combo gave me tons of energy and was the only "sweet" food I ate during the week, so I looked forward to working out. Post run I ate sweet potatoes, and pre-run was a simple egg and bacon breakfast usually, with my 1 cup of coffee (added coconut milk for good fat). I found this combo to be the best one for me to sustain energy during long runs. In case you're wondering, I always carried salt sticks, and two tapioca crepes in my pack. Additional easy grabs for unexpected long runs were pre-packaged baby food in the foil packs at stores like Target. be careful because sometimes these have alot of added sugars, but the right brand will have pureed sweet potatoes, apples, pears, etc. and that's it. These were life-savers for quick grabs.
Hope this helps and good luck!