An air/fuel ratio system would seem to be necessary to me. If nobody could tell me definitively, I'd start pig rich at 140% of the gasoline jet area (.7854 x bore x bore) and lean down until I got the right mix according to the A/F gauge. Correct A/F ratio for E85 is 9.8:1
Aem Electronics 30 5143 E85 Wideband Air Fuel Gauge 5 7 to 11 9 afr Analog | eBay

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