That 3.5 is going to be as fast as they get afaik. 3.5 is the lowest rated BL I have seen and just about every company has one. There are other numbers to look at when buying a motor like Kv and Kt. I haven't looked into what the "best" motor is, but look up all the 3.5's and see what you get. I think you are going to find a lot of them are very similar in spec. Which is why you get the responses that you did. It's like asking, "What do you think the best tasting soda is?"
As far as gear and top end speed, get the biggest pinion and the smallest spur you can find. Change over to 64p if you haven't already. It will give you more clearance to play with. 64p vs 48p spurs with the same tooth count are a lot smaller. But be aware that gearing your motor is important to it's life. I have not looked into it much, but a lot of people gear there motor by temp to give it the best life possible. Your FD is going to directly affect the rps the motor is at which will affect the temp. Now if you just making a few speed passes, I guess you'll be fine no matter what your FD is. But if it is going to be used for pro longed periods of time, keep an eye on the temps of both your esc and motor.
GL with your speed goal.
*Photon* *SC10 4x4*