What fool looks at top speed these days... no one is ever going to hit that fast, not even down Eastern creek straight lol. The change in FD imo is all based on it's purpose. You can get a shorter final drive which can be 'torquey' but maybe around wakefield it forces you to hold out the gear until the corner? Then you're f**ked lol. Also, with the street car, definitely gotta check if YOU can handle the cruising speed. A droney exhaust at 4.2k rpm is probably the worst thing I've ever experienced!