Apparently I was too quick to dismiss the possibility of it being a variable reluctance (inductive) sensor.
See this thread for additional discussion and other possible solutions.
http://ecomodder.com/forum/showthrea...zed-16518.html
I personally like the LM2907 solution but what works best for others could mostly depend on what parts they have on hand. Additional proven solutions give people more options so please do complete your write up when you have a chance.
Mike