being that i know of a converted a turbo SHO that used E85, i will share two detracting thoughts and one positive. pure ethanol has less lubricity i think, so it might wear out the injection pump and other parts gasoline may have a lubricating effect on, which might be expensive. also the side location of the injector may/will spray onto the cylinder wall and ethanol might wash down the oil film, leading to excessive engine wear. best case is that you may need to change the oil every 1000 miles for street use and weekly for race use. on the upside, you definitely could run more boost, spark timing, cam retard/advance and get more power.
I would add that alcohol cars should run colder spark plugs than stock too, in fact i would suggest to those 2010 SHO owners that get even an up-rated tune, to run the following spark plug, motorcraft AYFS092FEC, it is going to be discontinued very soon and its great on this engine, i would suggest to those lucky 2010 SHO owners to buy a few sets now.