This past year seems to be at 151 bushels per acre and 2.8 gallons per bushel for a total of 423.
The corn yield is from the link above for US 2007 harvest and the 2.8 is in the most recent RFA’s Ethanol Industry Outlook 2007.
http://www.ethanolrfa.org/objects/pdf/outlook/RFA_Outlook_2007.pdf
The National Corn Growers Association reports that plants now ocming on line squeeze out 2.9 gallons per bushel. The contracting of high starch corn will shortly push that figure to 3.0 gallons, which will make the arithmetic a lot easier for me.