I don't think that you will have any trouble making the 60 mile cutoff. You may be in for a suffer-fest after that though, because it will be something you haven't done before.
Here is what I recommend. You don't really want to lose weight (more than couple pounds) this late in the game. But try to eat healthy. When I am doing a century, I eat pasta for the last three nights before the ride. That will load you up with carbs. Eat a good, but fairly bland breakfast the day of the ride. I usually eat some pasta, fruit and cereal.
I use a CamelBak and put in one 16oz bottle of Gatorade and the rest water. If it is hot, I carry a water bottle full of straight Gatorade also. EAT AT THE REST STOPS. Even if you are not hungry, eat a bananna. Banannas also help prevent leg cramps. If you don't eat, you will bonk and ruin your day. Keep the rest stops short, 10-15 minutes. YOu do not want to start cooling down. Since you have been using gel packs, do that on the road. Drink pleanty.
So, that is my non-expert food advise. But, it is what works for me.
Like has been mentioned before, drafting will dramatically increase your speed, and reduce your energy output at the same time. Good luck. You'll do fine