|MadSci Network: Earth Sciences|
Sorry for the delay in answering your question. Unfortunately, this question has become even more relevant given the August 11, 1999 tornado that ripped through Salt Lake City.
According to statistics compiled between 1950 and 1989, 68% of recorded tornadoes ranked as either F0 or F1 on the Fujita Wind Damage Scale. By comparison, only 2% are ranked as F4 or F5.
F0 40-72 mph F1 73-112 mph F2 113-157 mph F3 158-206 mph F4 207-260 mph F5 261-318 mph
As far as the fastest speed ever recorded, my sources told me that this was achieved during the May 3, 1999 tornado outbreak in central Oklahoma. I was unable to find an actual wind speed, but it would be safe to say that it was around 300 mph. Also keep in mind that not all tornadoes have been "recorded". Therefore there have likely been tornadoes even stronger than this one.
Lots of information about the May 3 outbreak is available through the link above, so search around and you may be able to find the information you're looking for!
Try the links in the MadSci Library for more information on Earth Sciences.