Check the Regulation Guidance Library...
Hi David,
Focusing on the question "Are there any Continental o-200 configurations that make ethanol OK" A quick review of the Regulation Guidance Library (at www.faa.gov) limited to the Type Certificate Data Sheets (TCDS) and Supplemental Type Certificates (STC) for the 0-200A, B, C, D, and X show that 1). only avgas is approved as fuels and 2). there are no STC for ethanol. The EAA's STCs only allow "unleaded automotive gasoline, 87 minimum antiknock index, per ASTM Specification D-439 or D-4818 of any volatility class, A through E, or 82UL AVGAS per ASTM D-6227."
So the short answer is "no" for certificated aircraft and of course this does not apply to experimental aircraft.