Quite a few folks locally are using methonal under boost to increase the octane of the pump gas - its sprayed in seperately from the pump gas. It also cools the air down considerably, enough that folks are not running an intercooler.
As far as straight methonal, the injectors and fuel systems on the later model engines are typically M85 compliant from a materials point of view so its less of an issue. So 100% is probably doable with minor changes, I'd have to take a closer look at the fuel tanks on the M85 and see what there made out - most likely composite or S/S.
MAybe our Brazilian friends will chime in here they have been running 100% for over 30 years.
