Why would you ask Burton, they do nothing with bike engines...
Anyway, there's a good Excel based gear ratio calculator over on LCB. There's ratio data for a CBR1000 already loaded into it, you would have to check if that covers the 2004 model.
Anyway, you would need a 3.14:1 ratio to get a 124mph top speed if you're running a Sierra diff in combination with 195/50/15 tyres, with a 70mph cruise at 6200rpm. That's the rarest ratio for the Sierra, were only available on the 2.3 diesel and command a significant premium over other ratios. Good luck finding a LSD version, I can't see Ford doing a factory LSD for an oil burner. This would leave getting something like a Quaife LSD then transplanting it into a standard diff, which would cost you the best part of £1k to do, Burton sell the Quaife LSD for £650, you'd probably have to part with £200+ for a complete 3.14 diff and add sundries and assembly costs on top.
If you have a Mazda diff, the longest ratio is a 3.6:1 which is found in a few Torsens and the Super Fuji diffs. Gives a top speed of about 107mph with a 70mph cruise at 7200rpm.
HTH