Rather than dive into the motor, work it from the fuel side of the equation.
Find a programmable ECU solution and have a new fuel map tuned for E85.

An E85 map will need to be richer than the OEM map, so do not expect an increase in fuel economy. Also, keep in mind that you will not be able to run anything other than E85 after this tuning is completed.

Frankly, unless you've got a guaranteed supply of dirt cheap E85 for years, I wouldn't bother. The couple hundred you spend on an ECU retune will take months if not years to pay back.