I been using fuel with ethanol in my '81 R65 pretty much since 1983, other than a reduction in fuel mileage, in my case, about 10%, with 10% alcohol in the fuel supply locally since 1997.
I have not seen any degradation in the brass carb parts or floats .
The only OEM floats from Bing that are ' alcohol ' resistant, are the independent floats, with the price of the kit, I would not recommend it .