An interesting read on the conductivity of E85:Mud Flap wrote: My final concern as of recent is the fuel level sending unit in the tank. Even new ones are only built for gas it seems. E85 conducts electricity which is why E85 gas tanks are equipped with arc-proof sending units and flame-arresters in the fill neck. The fuel pump will have to be the same way. I'm not using the stock gas tank, I'm at least buying a new stock tank, but I'm considering opening up the old tank and taking the top sheetmetal off to make a tub, sealing it, and using it as a base to hold a fuel cell in the trunk. It'll only be $50-100 more than a stock tank anyways, I'm still considering it.
http://foreinnovations.blogspot.com/201 ... s.html?m=1
It seems that even glass is more conductive than E85, which is only slightly more conductive than gasoline (which is to say, pretty much not a conductor).
As for the stock tank, you can pick up a 1970 22gal tank for about $125 from Mustangs Unlimited, which includes a sending unit. I did this just this week, and welded a rear mount sump on it as well. I honesty don't have any concerns as far as the sending unit goes...but will do some more specific research on that point.
I'm going to be using E85 for my Cougar as well, and have done a TON of research on it over the last months. I'm going to run a Megasquirt MS3x system instead of a carb, in order to take full control of my fuel and timing curve to get the most out of the fuel. Feel free to get ahold of me if you find out anything interesting regarding running this fuel, or have any questions regarding what I'm doing with my build .