I think most can be converted for ethanol, though I don't know what the cost might be. I think it mostly relates to seals and gaskets since ethanol is more corrosive than gasoline.
I know you can use a gas/methanol mixture (something like 80/20) without any modifications. They were selling the methanol blend at the pump in Wyoming back in the late eighties, and I used to get it because it was 5 cents cheaper per gallon (back in the 85�¢/gal days). However, I don't know if you can run pure methanol in an unmodified engine or not.
I also know that bio-diesel will run on unmodified engines, but to run a diesel on pure vegetable oil there are some required mods.
