It's best to gear it so that your motor temps stay in check during your run, not for a certain speed (unless you're just making a quick speed run, then stopping). I had a 20T pinion on my Muggy when I first built it and that yielded some awesome speeds but I was pushing 150+ on my Neu after 5 minutes. Dropped down to a 13T pinion and now it is running 140 after 20 minutes.
Running 4s through an ESC only designed for 3s (don't let Patrick find out, he'll yell at you

) and pulling the amps you're pulling with that thing you definitely need a fan. Even just a little 25mm Novak fan will dramatically lower temps. I'd go for a nice 12v computer fan and solder it to the battery leads on the ESC though. The capacitor mod will also drop temps, so that combined with the fan and you should be in business.