I assume that your 3.4Kv actualy means 3400 Kv?, there are a bigger range of brushless motors with different Kvs compared to brushed motors, picking an appropriate motor is much easier I thing, turns, what the hell is turns
( of course i do know) most wouldn't have a clue
i had a Novak 5300 in the car slow running seemed fast
Thats 5300Kv, at 7.2 volts its no load speed is 38000 RPM, the 3400 Kv is 24400 Rpm,
You need something around the 1000 Kv to 1500 Kv, that will give good slow speed as well as reasonable speed at full throttle
Nick