Just remember a couple things in trying to hit your speed goal.
1) Voltage x kv rating = unloaded RPM (ie: a 5700 kv motor on 3 cells I'll use 8v per cell = 136,800 RPM before the load.)
2) How many RPMs can your tires and other equipment handle?
3) How many "Tire" RPMs do you need to spin to go 100 mph?
a 2.4 inch diameter tire (NOTE: Most tires will grow at RPM) is 0.62832 ft.
100 mph = 528,000 ft. per hour
Your 2.4" tire will need to "average" 840,336.13 Rotations per hour (divided by 60 for Tire RPM = 14,005.6)
So now your 5700 kv motor on 3 cell (24 volts) turning 136,800 RPM before the load needs to turn the tires 14,005.6 RPMs - so factor in your Sedans internal gear ratio (let's say it's 2.5:1) that gets you down to 54720 RPMs - which would put you at about a 3.90 Pinion/Spur ratio. to start with...or around 81/21 (48 pitch gears)
This is just 'Ball Park' info - note that using a BOOSTED Esc adds a different calculation because of increased RPM and Amp Load - the type of Aero adds Drag and Amp Load - which are all things you fine tune after a few easy runs.
AERO Blow Overs - Tire Blow Offs - Over Gearing/Voltage Calculations - Too Much Steering End Point are all things to consider and plan for.
When you wanna go REALLY Fast - build one of these Like NIC did.
http://rossa.org.uk/