You could beat that truck on gasoline if you know how to keep the tires planted. That's going to be a big problem for him, depending on his tires, keeping that axle planted at launch. If he's smart you'll see a few hundred pounds of weight back there.
You're not going to see much benefit of using E85 if you get down to a 1/4 tank, fill it up, run it down to 1/4 tank and race the guy. At best, you'll be in the 50% alcohol content range and the truck will not really have had time enough to fully adjust to it. Run another tank if you can or drive it 50 miles more after the light comes on to get that alcohol content up as high as possible (83%).
Either one of you have 4 wheel drive? If so, plan accordingly.