to make our current cars to take e85 we need:

Bigger gas tank (to keep the same disctance per tank)
Stainless steel lines and injector rails (85 is very corrosive)

now to run efficient you need:
Tune for the E85
you FI guys will love this- up your boost, E85 is more like 115 Octane. Upping the boost will get you more power and be more efficient.