Befor you do this, check out the mpg drop you get with E85
(EPA of 2008 chevy impala flex fuel) it drops from 29mpg on gasoline to 21mpg on E85, add to that the recent study that shows that ethonal contributes more to global warming then gasoline, that it takes half a gallon of oil to produce the ferterlizer and pestisides that are used in growing corn, and nearly as much fuel (gas, diesel, natural gas) to farm, haul, and prosese the corn into alcohol that it is close to being a net loss, add to that the economic side of it, that a recent servy (radio news broadcast) of economists say that bio-fuels are bad for the economy because of how they displace food production and drive up food prices.
anyway, to convert your engine to run on alcohol (E85) you need to rase the compression, give it a ritcher mix of fuel, and replace your plastic and rubber parts so they will not be attacted by the higher amount of alcohol.
to make a flex fuel vehicle (straight gas, or E85) you need to do all the stuff that is needed just for E85, plus add/replace a number of sensors and maybe the cars computer so that it can tell what fuel it has, and self adjust for those fuels.
The main reason for having to do all of this is that an alcohol burning engine is differnt then a gasoline burning engine, yes some can burn both, but not well, just like our A/C delco light plant can burn gasoline or kerosen or maybe even bacon greese, but not well, and not without alot of manual adjustments.