IMHO, aluminum fuel tanks should be fabricated of at least series 5052 material. This is a marine grade aluminum that is more resistant to corrosion than other series aluminum. The fuel tank should be coated on the exterior with an epoxy paint (best), although I have done mine with Zinc Chromate (sufficient). The problem with ethanol blended gasoline is phase seperation during long term storage. Layers of alcohol, gasoline and water will form, with the water residing at the bottom of the tank causing corrosion. If the car is regularly used, this should not present a problem, however, long term storage may. Use a fuel stabilizer such as Sta-Bil will help. Best to keep the tank either full and use it, or empty and dry (best) for storage. In any case, most aluminum fuel tanks will withstand ethanol fairly well. Another concern that is mostly not thought of, is the Ethanol and water will provide for galvanic corrosion to both the tank and brass or copper fittings to the detrement of the aluminum. Avoid these. Stainless steel or aluminum fittings should cause no problems.
Should you be overly concerned, you can always coat the inside of the tank with an epoxy sealer.
As mentioned in an earlier thread, seals, gaskets and hoses not rated for ethanol will be degraded. Forgot to mention gaskets and seals for sending units!
Remember, this IHMO, but I have designed many, many fuel tanks..