So if you just want a theoretic top speed as in " I have a 3.27 rear end so my top speed is 202mph." Just raise you`re rev limiter to 50,000 RPM. In theory you could probably hit the speed of sound in 4th
P.S. I did not do the math, but it`s just a joke in the first place.
Now in seriousness, To actually raise your realistic top speed, their isn`t much else that can be done, other then power, gearing and aero.