There really is no breed that is the fastest. If there was every body would have ludo's birds, or Clausing's houbens. All you can do is watch the race sheets, find the flyer that wins the most at the kind of race you would be interested in and get those birds.
Consider race birds BASE speed has been figured at 45 miles per hour. NOw with tail winds and sperts one can fly faster. But base is 45 miles per hour. Can other pigeons fly that fast yes They can. How long well not sure.