I think this is something that varies drastically by person. Depending on how many calories you burn, you'll need more or less during the race. One thing I would suggest is thinking in terms of time rather than miles to gauge when to eat. For marathons at sea level, I find one gel per hour is a good ratio for me. I was able to apply this for Pikes as well. But remember, you'll be running on Pikes much longer than you would for the same distance at sea level. So, if you need 1 gel for 13 miles at sea level, you're probably going to need about 3 to do the 13 mile Ascent. If your stomach doesn't love gels, it might not take that. Also, you might need to take in some protein at that point to keep your energy up. The best test will be to practice different food options on your long runs/hikes. The aid stations typically have pretzels and M&M's and a few other snacks... but I don't recommend getting to the A-frame, realizing you are starving because you didn't plan your calories well enough, and deciding to test M&M's for the first time. You might end up seeing them again a mile later if your body doesn't handle that well. And altitude might make your stomach much more sensitive than usual.
