OK....have done a lot of research on this and have found what may be the correct answer to the "two post" problem. The article I read said that for that year of sensor it had two posts because it could be used for the Ford V-8 that had another sensor on the other side of the block. This other sensor wire ran back to the main one that went to the dash gauge. Sounds kinda hinkie to me but it's the best explanation I've heard....BUT....I never heard of an engine that required two sensors either? So....anybody else want to take a shot at this? I'm just running the one wire and probably could have used a '56 or '57 sensor at a third of the price.