I have recently converted an LX to brushless. I haven't had the weather to really run it yet. I went with the Novak conversion kit 6.5 3400kv (mostly because it was a kit) no real major building. Based on what Novak has to say I'm going to be running a 11 /47(metal to metal). Once the snow melts I will have more info. But I do think temp is going to determine your gearing options. Mine is a 4s setup (I have had good luck with Maxamps 6000mah).
It won't be til may before I hit the track with it...So if you get your build done before then....Do tell. My local track has a 4s lipo limit, but I would love to hear how a 6s LX goes/holds up. I still run a gas lx with a .28 nitro and the diffs are high maintenance.
Heres a pic