There is alot of information out there, but I'll cover some of the basics:
100 R+M/2 Octane
High latent heat of vaporization, 840 to gas's 350 kJ/kg - This is where the slight bump in power comes from, air temperatures @ the intake valve are lower as the mixture evaporates.
About half the energy content of gas, 29 compared to 44MJ/kj.
Stoich is lower, 9.8:1 compared to 14.7:1. You will need a fuel system that is capable of supplying ~33% additional fuel. Alcohol likes to eat or disform (swell) certain rubber and seals, Viton and Teflon should be considered for prolonged use.